Brigham Young University N283 Eyring Science Center Provo, UT 84602
Popular version of paper 2pAAa10, “High-resolution measurements of speech directivity” Presented Tuesday afternoon, November 3, 2015, 4:40 PM, Grand Ballroom 3 170th ASA Meeting, Jacksonville
Introduction In general, most sources of sound do not radiate equally in all directions. The human voice is no exception to this rule. How strongly sound is radiated in a given direction at a specific frequency, or pitch, is called directivity. While many [references] have studied the directivity of speaking and singing voices, some important details are missing. The research reported in this presentation measured directivity of live speech at higher angular and frequency resolutions than have been previously measured, in an effort to capture the missing details.
Measurement methods The approach uses a semicircular array of 37 microphones spaced with five-degree polar-angle increments, see Figure 1. A subject sits on a computer-controlled rotating chair with his or her mouth aligned at the axis of rotation and circular center of the microphone array. He or she repeats a series of phonetically-balanced sentences at each of 72 five-degree azimuthal-angle increments. This results in 2522 measurement points on a sphere around the subject.
[MISSING Figure 1. A subject and the measurement array]
Analysis The measurements are based on audio recordings of the subject who tries to repeat the sentences with exactly the same timing and inflection at each rotation. To account for the inevitable differences in each repetition, a transfer function and the coherence between a reference microphone near the subject and a measurement microphone on the semicircular array is computed. The coherence is used to examine how good each measurement is. The transfer function for each measurement point makes up the directivity. To visualize the results, each measurement is plotted on a sphere, where the color and the radius of the sphere indicate how strongly sound is radiated in that direction for a given frequency. Animations of these spherical plots show how the directivity differs for each frequency.
[MISSING Figure 2. Balloon plot for male speech directivity at 500 and 1000 Hz.] [MISSING Figure 3. Balloon plot for female speech directivity at 500 and 1000 Hz.] [MISSING Animation 1. Male Speech Directivity, animated] [MISSING Animation 2. Female Speech Directivity, animated]
Results and Conclusions Some unique results are visible in the animations. Most importantly, as frequency increases, one can see that most of the sound is radiated in the forward direction. This is one reason for why it’s hard to hear someone talking in the front of a car when you’re sitting in the back, unless they turn around to talk to you. One can also see in the animations that as frequency increases, and most of the sound radiates forwards, there is poor coherence in the back area. This doesn’t necessarily indicate a poor measurement, just poor signal-to-noise ratio, since there is little sound energy in that direction. It’s also interesting to see that the polar angle of the strongest radiation also changes with frequency. At some frequencies the sound is radiated strongly downward and to the sides, but at other frequencies the stound is radiated strongly upwards and forwards. Male and female directivities are similar in shape, but at different frequencies, since the fundamental frequency of males and females is so different.
A more complete understanding of speech directivity has great benefits to several industries. For example, hearing aid companies can use speech directivity patterns to know where to aim microphones in the hearing aids to pick up the best sound for the hearing aid wearer having a conversation. Microphone placement in cell phones can be adjusted to get clearer signal from those talking into the cell phone. The theater and audio industries can use directivity patterns to assist in positioning actors on stage, or placing microphones near the speakers to record the most spectrally rich speech. The scientific community can develop more complete models for human speech based on these measurements. Further study on this subject will allow researchers to improve the measurement method and analysis techniques to more fully understand the results, and generalize them to all speech containing similar phonemes to those in these measurements.
Please keep in mind that the research described in this Lay Language Paper may not have yet been peer reviewed.
Transit centered living relies on amenities close to home; mixing multifamily residential units with professional, retail and commercial units on the same site. Use the nearby trains to get to work and out, but rely on the immediate neighborhood, even the lobby for errands and everyday needs. Transit centered living is appealing as it eliminates the need for sitting in traffic, seems good for the environment and adds a sense of security, aerobic health and time-saving convenience. Include an on-site fitness center and residents don’t even have to wear street clothes to get to their gym!
Developers know that a state-of-the-art fitness center is icing on their multifamily residence cake as far as attracting buyers. Gone is the little interior room with a couple treadmills and a stationary bike. Today’s designs include panoramic views, and enough ellipticals, free weights, weight & strength machines, and shower rooms to fill 2500-4000 square feet, not to mention the large classes offered with high energy music and an enthusiastic leader with a microphone. The increased focus on maintaining aerobic health, strength and mobility is fantastic, but the noise and vibration it generates? Not so great. Sometimes cooperative scheduling keeps the peace, but often residents will want to have access to their fitness center at all hours, so wise project leaders involve a noise control engineer early in the design process to develop a fitness center next to which everyone will want to live.
Remember the string and two empty cans? Stretch the string taut and conversations can travel the length of the string, but pinch the string and the system fails. As noise travels through all kinds of structures and through the air as well, it is the design goal of the noise and vibration experts to prevent that transmission. Airborne noise control can be effective using a combination of layered gypsum board, fiberglass batt insulation, concrete and resilient framing members that absorb the sound rather than transmit it through a wall or a floor/ceiling system. Controlling the structure borne noise and vibration can involve much thicker rubber mats, isolated concrete slabs and a design that incorporates the structural engineer’s input on stiffening the base building structure. And it’s not simply noise that the design is intended to restrict, it is silent, but annoying vibrations as well.
Reducing the floor shaking impact of dropping barbells on the ground is the opposite of hearing a pin drop. Heavy, steel plates loaded on a barbell, lifted 6-8 feet off the ground and then dropped. Repeatedly. Nobody wants to live under that, so designers think location, location, location. But big windows are pointless in the basement, so something has to go under the fitness center. Garage space, storage units or mechanical rooms won’t mind the calisthenics above them. And sometimes the overall design of the building structure, whether it be high-rise with underground parking, Texas wrap building (u-shaped building with elevated parking garage on interior.), or a podium style building can offer an ideal location for this healthy necessity.
It’s not an acoustical trade secret that the best method of noise control is at the source so consider what makes the noise. Manufacturers have met the demand for replacing the old standard graduated barbell steel plates for free weight combinations with a rubber/urethane coated steel weight. These weights make much less noise when impacting each other, but are still capable of generating excessive structure-borne noise levels. This is a great example of controlling both air borne (plates clanking together) and structure borne (barbells impacting the floor) transmission paths. Speakers and sound systems and the wall/floor/ceiling systems can work together to offer clarity and quality to listeners and limitations for what the neighbors will hear, but it takes expertise and attention.
Disregarding the recommendations of noise and vibration professionals can result in an annoying, on-site gym that brings stressful tension and ongoing conflict, nothing that promotes healthy well-being.
Foresight in design and attention to acoustical specs on building materials, under the direction of a noise and vibration engineer, assures a fitness center that is a pleasant, effective space for fitness and social opportunities, an asset to the transit centered neighborhood. Do everyone a favor and pay attention to good design and product specification early on; that’s sound advice.
John Mourjopoulos – mourjop@upatras.gr University of Patras Audio & Acoustic Technology Group, Electrical and Computer Engineering Dept., 26500 Patras, Greece
Historical perspective The ancient open amphitheatres and the roofed odeia of the Greek-Roman era present the earliest testament of public buildings designed for effective communication of theatrical and music performances over large audiences, often up to 15000 spectators [1-4]. Although mostly located around the Mediterranean, such antique theatres were built in every major city of the ancient world in Europe, Middle East, North Africa and beyond. Nearly 1000 such buildings have been identified, their evolution starting possibly from the Minoan and archaic times, around 12th century BC. However, the known amphitheatric form appears during the age that saw the flourishing of philosophy, mathematics and geometry, after the 6th century BC. These theatres were the birthplace of the classic ancient tragedy and comedy plays fostering theatrical and music activities for at least 700 years, until their demise during the early Christian era. After a gap of 1000 years, public theatres, opera houses and concert halls, often modelled on these antique buildings, re-emerged in Europe during the Renaissance era.
During the antiquity, open theatres were mainly used for staging drama theatrical performances so that their acoustics were tuned for speech intelligibility allowing very large audiences to hear clearly the actors and the singing chorus. During this era, smaller sized roofed versions of these theatres, the “odeia” (plural for “odeon”), were also constructed [4, 5], often at close vicinity to open theatres (Figure 1). The odeia had different acoustics qualities with strong reverberation and thus were not appropriate for speech and theatrical performances but instead were good for performing music functioning somehow similarly to modern-day concert halls.
Figure 1: representation of buildings around ancient Athens Acropolis during the Roman era. Besides the ancient open amphitheatre of Dionysus, the roofed odeion of Pericles is shown, along with the later period odeion of Herodes (adopted from www.ancientathens3d.com [6]).
Open amphitheatre acoustics for theatrical plays The open antique theatre signifies the initial meeting point between architecture, acoustics and the theatrical act. This simple structure consists of the large truncated-cone shaped stepped audience area, (the amphitheatrical “koilon” in Greek or “cavea” in Latin), the flat stage area for the chorus (the “orchestra”) and the stage building (the “skene”) with the raised stage (“proskenion”) for the actors (Figure 2).
Figure 2: structure of the Hellenistic period open theatre.
The acoustic quality of these ancient theatres amazes visitors and experts alike. Recently, the widespread use of acoustic simulation software and of sophisticated computer models has allowed a better understanding of the unique open amphitheatre acoustics, even when the theatres are known solely from archaeological records [1,3,7,9,11]. Modern portable equipment has allowed state-of-the-art measurements to be carried out in some well-preserved ancient theatres [8,10,13]. As a test case, the classical / Hellenistic theatre of Epidaurus in southern Greece is often studied which is famous for its near-perfect speech intelligibility [12,13]. Recent measurements with audience present (Figure 3) confirm that intelligibility is retained besides the increased audience sound absorption [13].
Figure 3: Acoustic measurements at the Epidaurus theatre during recent drama play (form Psarras et al.[13]).
It is now clear that the “good acoustics” of these amphitheatres and especially of Epidaurus, is due to a number of parameters: sufficient amplification of stage sound, uniform spatial acoustic coverage, low reverberation, enhancement of voice timbre, all contributing to perfect intelligibility even at seats 60 meters away, provided that environmental noise is low. These acoustically important functions are largely a result of the unique amphitheatrical shape: for any sound produced in the stage or the orchestra, the geometric shape and hard materials of the theatre’s surfaces generate sufficient reflected and scattered sound energy which comes first from the stage building (when this exists), then the orchestra floor and finally from the surfaces at the top and back of seat rows adjacent each listener position and which is uniformly spread to the audience area [11,13] (see Figure 4 and Figure 5).
Figure 4: Acoustic wave propagation 2D model for the Epidaurus theatre. The blue curves show the direct and reflected waves at successive time instances indicated by the red dotted lines. Along with the forward propagating wavefronts, backscattered and reflected waves from the seating rows are produced (from Lokki et al. [11]).
This reflected sound energy reinforces the sound produced in the stage and its main bulk arrives at the listener’s ears very shortly, typically within 40 milliseconds after the direct signal (see Figure 5). Within such short intervals, as far as the listeners’ brain is concerned, this is sound also coming from the direction of the source in the stage, due to a well-known perceptual property of human hearing, often referred to as “precedence or Haas effect” [11,13].
Figure 5: Acoustic response measurement for the Epidaurus theatre, assuming that the source emits a short pulse and the microphone is at a seat at 15 meters. Given that today the stage building does not exist, the first reflection arrives very shortly from the orchestra ground. Seven successive and periodic reflections can be seen from the top and the risers of adjacent seat rows. Their energy is reduced within approx. 40 milliseconds after the arrival of the direct sound (from Vassilantonopoulos et al. [12]).
The dimensions for seating width and riser height, as well as the koilon slope, can ensure minimal sound occlusion by lower tiers and audience and result to the fine tuning of in-phase combinations of the strong direct and reflected sounds [9,11]. As a result, frequencies useful for speech communication are amplified adding a characteristic coloration of voice sound and further assisting clear speech perception [11]. These specific amphitheatre design details have been found to affect the qualitative and quantitative aspects of amphitheatre acoustics and in this respect, each ancient theatre has unique acoustic character. Given that the amphitheatric seating concept evolved from earlier archaic rectangular or trapezoidal shaped seating arrangements with inferior acoustics (see Figure 6), such evolution hints at possible conscious acoustic design principles employed by the ancient architects. During the Roman period, stage building grew in size and the orchestra was truncated, showing adaptation to artistic, political and social trends with acoustic properties correlated to intended new uses favouring more the visual performance elements [4,15]. Unfortunately, only few fragments of such ancient acoustic design principles have been found and only via the writings of the Roman architect Marcus Vitruvius Pollio (70-15 BC), [14].
Figure 6: Evolution of the shape of open theatres. Roman period theatres had semi-circular orchestra and taller and more elaborate stage building.The red lines indicate the koilon / orchestra design principle as described by the ancient architect Vitruvius.
The acoustics of odeia for music performances Although the form of ancient odeia broadly followed the amphitheatric seating and stage / orchestra design, they were covered by roofs usually made from timber. This covered amphitheatric form was also initially adopted by the early Renaissance theatres, nearly 1000 years after the demise of antique odeia [16] (Figure 7).
Figure 7: Different shapes of roofed odeia of antiquity and the Renaissance period (representations from www.ancientathens3d.com [6]).
Supporting a large roof structure without any inner pillars over the wide diameter dictated by the amphitheatric shape, presents even today a structural engineering feat and it is no wonder that odeia roofs are not preserved. Without their roofs, these odeia appear today to be similar to the open amphitheatres. However, computer simulations indicate that in period, unlike the open theatres, they had strong acoustic reverberation and their acoustics helped the loudness and timbre of musical instruments at the expense of speech intelligibility, so that these spaces were not appropriate and were not used for theatrical plays [4,5]. For the case of the Herodes odeion in Athens (Figure 8), computer simulations show that the semi-roofed version had up to 25% worst speech intelligibility compared to the current open state, but the strong acoustic reverberation which was similar to a modern concert hall of compatible inner volume of 10000 m3, made it suitable as a music performance space [5].
Figure 8: The Herodes odeion at its current state and via computer model of the current open and its antique semi-roofed version. (from Vassilantonopoulos et al. [5]). Very recent archaeological evidence indicates that the roof covered fully the building, as is also shown in Figure 10.
Thousand years ago, these antique theatres established acoustic functionality principles that even today prevail for the proper presentation of theatre and music performances to public audiences and thus signal the origins of the art and science in building acoustics.
References [1] F. Canac, “L’acoustique des théâtres antiques”, published by CNRS, Paris, (1967). [2] R. Shankland, “Acoustics of Greek theatres”, Physics Today, (1973). [3] K. Chourmouziadou, J. Kang, “Acoustic evolution of ancient Greek and Roman theatres”, Applied Acoustics vol.69 (2008). [4] G. C. Izenur, “Roofed Theaters of Classical Antiquity”, Yale University Press, New Haven, Connecticut, (1992). [5] S. Vassilantonopoulos, J. Mourjopoulos, “The Acoustics of Roofed Ancient Odea”, Acta Acoustica united with Acustica, vol.95, (2009). [6] D. Tsalkanis, www.ancientathens3d.com, (accessed April 2015). [7] S. L. Vassilantonopoulos, J. N. Mourjopoulos, “A study of ancient Greek and Roman theater acoustics”, Acta Acustica united with Acustica 89 (2002). [8] A.C. Gade, C. Lynge, M. Lisa, J.H.Rindel, “Matching simulations with measured acoustic data from Roman theatres using the ODEON programme”, Proceedings of Forum Acusticum 2005, (2005). [9] N. F. Declerq, C. S. Dekeyser, “Acoustic diffraction effects at the Hellenistic amphitheatre of Epidaurus: Seat rows responsible for the marvellous acoustics”, J. Acoust. Soc. Am. 121 (2007). [10] A. Farnetani, N. Prodi, R. Pompoli, “On the acoustics of ancient Greek and Roman theatres”, J. Acoust. Soc. Am. 124 (2008). [11] T. Lokki, A. Southern, S. Siltanen, L. Savioja, “Studies of Epidaurus with a hybrid room acoustics modelling method”, Acta Acustica united with Acustica, vol.99, 2013. [12] S. Vassilantonopoulos, T. Zakynthinos, P. Hatziantoniou, N.-A. Tatlas, D. Skarlatos, J. Mourjopoulos, “Measurement and analysis of acoustics of Epidaurus theatre” (in Greek), Hellenic Institute of Acoustics Conference, (2004). [13] S. Psarras, P. Hatziantoniou, M. Kountouras, N-A. Tatlas, J. Mourjopoulos, D. Skarlatos, “Measurement and Analysis of the Epidaurus Ancient Theatre Acoustics”, Acta Acustica united with Acustica, vol.99, (2013). [14] Vitruvius, “The ten books on architecture” (translated by Morgan MH), London / Cambridge, MA: Harvard University Press, (1914). [15] Beckers, Benoit, N.Borgia, “The acoustic model of the Greek theatre.” Protection of Historical Buildings, Prohitech09, (2009). [16] M. Barron, “Auditorium acoustics and architectural design”, London: E& FN Spon (1993).
“Natural” Sounds Improves Mood and Productivity, Study Finds
Work presented at the 169th Acoustical Society of America (ASA) Meeting in Pittsburgh may have benefits from the office cube to the in-patient ward
WASHINGTON, D.C., May 19, 2015 — Playing natural sounds such as flowing water in offices could boosts worker moods and improve cognitive abilities in addition to providing speech privacy, according to a new study from researchers at Rensselaer Polytechnic Institute. They will present the results of their experiment at the 169th Meeting of the Acoustical Society of America in Pittsburgh.
An increasing number of modern open-plan offices employ sound masking systems that raise the background sound of a room so that speech is rendered unintelligible beyond a certain distance and distractions are less annoying.
“If you’re close to someone, you can understand them. But once you move farther away, their speech is obscured by the masking signal,” said Jonas Braasch, an acoustician and musicologist at the Rensselaer Polytechnic Institute in New York.
Sound masking systems are custom designed for each office space by consultants and are typically installed as speaker arrays discretely tucked away in the ceiling. For the past 40 years, the standard masking signal employed is random, steady-state electronic noise — also known as “white noise.”
Braasch and his team had previously tested whether masking signals inspired by natural sounds might work just as well, or better, than the conventional signal. The idea was inspired by previous work by Braasch and his graduate student Mikhail Volf, which showed that people’s ability to regain focus improved when they were exposed to natural sounds versus silence or machine-based sounds.
Recently, Braasch and his graduate student Alana DeLoach built upon those results in a new experiment. They exposed [HOW MANY??] human participants to three different sound stimuli while performing a task that required them to pay close attention: typical office noises with the conventional random electronic signal; an office soundscape with a “natural” masker; and an office soundscape with no masker. The test subjects only encountered one of the three stimuli per visit.
The natural sound used in the experiment was designed to mimic the sound of flowing water in a mountain stream. “The mountain stream sound possessed enough randomness that it did not become a distraction,” DeLoach said. “This is a key attribute of a successful masking signal.”
They found that workers who listened to natural sounds were more productive than the workers exposed to the other sounds and reported being in better moods.
Braasch said using natural sounds as a masking signal could have benefits beyond the office environment. “You could use it to improve the moods of hospital patients who are stuck in their rooms for days or weeks on end,” Braasch said.
For those who might be wary of employers using sounds to influence their moods, Braasch argued that using natural masking sounds is no different from a company that wants to construct a new building near the coast so that its workers can be exposed to the soothing influence of ocean surf.
“Everyone would say that’s a great employer,” Braasch said. “We’re just using sonic means to achieve that same effect.”
WORLDWIDE PRESS ROOM In the coming weeks, ASA’s Worldwide Press Room will be updated with additional tips on dozens of newsworthy stories and with lay language papers, which are 300 to 500 word summaries of presentations written by scientists for a general audience and accompanied by photos, audio and video. You can visit the site during the meeting at https://acoustics.org/world-wide-press-room/.
PRESS REGISTRATION We will grant free registration to credentialed journalists and professional freelance journalists. If you are a reporter and would like to attend, contact AIP Media Services at media@aip.org. For urgent requests, staff at media@aip.org can also help with setting up interviews and obtaining images, sound clips, or background information.
ABOUT THE ACOUSTICAL SOCIETY OF AMERICA The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world’s leading journal on acoustics), JASA Express Letters, Proceedings of Meetings on Acoustics, Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. See https://acousticalsociety.org/.
Background Music has the potential to evoke powerful emotions, both positive and negative. When listening to an enjoyable piece or song, an individual can experience intense, pleasurable “chills” that signify a surge of dopamine and activations in certain regions in the brain, such as the ventral striatum1 (see Fig. 1). Conversely, regions of the brain associated with negative emotions, for instance the parahippocampal gyrus, can activate during the presentation of music without harmony or a distinct rhythmic pattern2. Prior research has shown that the nucleus accumbens (NAcc) in the ventral striatum specifically activates during reward processing3, even if the stimulus does not present a tangible benefit, such as that from food, sex, or drugs4-6.
Figure 1: A cross-section of the human brain detailing (left) the ventral striatum, which houses the nucleus accumbens (NAcc), and (right) the parahippocampal gyrus.
Even subtle changes in acoustic (sound) stimuli can affect experiences positively or negatively. In terms of concert hall design, the acoustical characteristics of a room, such as reverberance, the lingering of sound in the space, contribute significantly to an individual’s perception of music, and in turn influences room acoustics preference7-8. As with the case for music, different regions of the brain should activate depending on how pleasing the stimulus is to the listener. For instance, a reverberant stimulus may evoke a positive emotional response in listeners that appreciate reverberant rooms (e.g. a concert hall), while negative emotional regions may be activated for those that prefer drier rooms (e.g. a conference room). The identification of which regions in the brain are activated due to changes in reverberance will provide insight for future research to investigate other acoustic attributes that contribute to preference, such as the sense of envelopment.
Methods
Stimuli The acoustic stimuli presented to the participants ranged in levels of perceived reverberance from anechoic to very reverberant conditions, e.g. a large cathedral. Example stimuli, which are similar to those used in the study, can be heard using the links below. As you listen to the excerpts, pay attention to how the characteristics of the sound changes even though the classical piece remains the same.
Example Reverberant Stimuli:
Short
Medium
Long
The set of stimuli with varying levels of reverberation were created by convolving an anechoic recording of a classical excerpt with a synthesized impulse response (IR) that represented the IR of a concert hall. The synthesized IR was double-sloped (see Fig. 2a) such that early part of the response was consistent between the different conditions, but the late reverberation differed. As shown in Fig. 2b the late parts of the IR vary greatly, while the first 100 milliseconds overlap. The reverberation times (RT) of the stimuli varied from 0 to 5.33 seconds
Figure 2: Impulse responses for the four synthesized conditions: (L) the total impulse response, (R) Time scale from 0 to 1 seconds to highlight the early part of the IR.
Functional magnetic resonance imaging (fMRI) was used to locate the regions of the brain that were activated by the stimuli. In order to find these regions, the images obtained due to the musical stimuli are each compared with the activations resulting due to control stimuli, which for this study were noise stimuli. Examples of control stimuli that are matched to the musical ones provided earlier can be heard using the links below. The noise stimuli were matched to have the same rhythm and frequency content for each reverberant condition.
Example Noise Stimuli:
Short
Medium
Long
Experimental Design A total of 10 stimuli were used in the experiment: five acoustic stimuli and five corresponding noise stimuli, and each stimulus was presented eight times. Each stimulus presentation lasted for 16 seconds. After each presentation, the participant was given 10 seconds to rate the stimulus in terms of preference on a five-point scale, where -2 was equal to “Strongly Dislike,” 0 was “Neither Like Nor Dislike,” and +2 was “Strongly Like.”
Results The following data represent the results of one participant averaged over the total number of repeated stimuli presentations. The average preference ratings for the five musical stimuli are shown in Fig. 3. While the majority of the ratings were not statistically different, the general trend is that the preference ratings were higher for the stimuli with the 1-2 second RTs and lowest for the excessively long RT of 5.33 seconds. These results are consistent with a pilot study that was run with seven subjects, and in particular, the stimulus with the 1.44 second RT was found to have the highest preference rating.
Figure 3: Average preference ratings for the five acoustic stimuli.
The fMRI results were found to be in agreement for the highest rated stimulus with an RT of 1.44 seconds. Brain activations were found in regions shown to be associated with positive emotions and reward processing: the right ventral striatum (p<0.001) (Fig. 4a) and the left and right amygdala (p<0.001) (Fig. 4b). No significant activation were found in regions shown to be associated with negative emotions for this stimulus, which supports the original hypothesis. In contrast, a preliminary analysis of a second participant’s results possibly indicates that activations occurred in areas linked to negative emotions for the lowest-rated stimulus, which is the one with the longest reverberation time of 5.33 seconds.
Figure 4: Acoustic Stimulus > Noise Stimulus (p<0.001) for RT = 1.44 s showing activation in the (a) right ventral striatum, and (b) the left and right amygdala.
Conclusion A first-level analysis of one participant exhibited promising results that support the hypothesis, which is that a stimulus with a high preference rating will lead to activation of regions of the brain associated with reward (in this case, the ventral striatum and the amygdala). Further study of additional participants will aid in the identification of the neural mechanism engaged in the emotional response to stimuli of varying reverberance.
References: 1. Blood, AJ and Zatorre, RJ Intensely pleasurable responses to music correlate with activity in brain regions implicated in reward and emotion. PNAS. 2001, Vol. 98, 20, pp. 11818-11823.
2. Blood, AJ, et al. Emotional responses to pleasant and unpleasant music correlate with activity in paralimbic brain regions. Nature Neuroscience. 1999, Vol. 2, 4, pp. 382-387.
3. Schott, BH, et al. Mesolimbic functional magnetic resonance imaging activations during reward anticipation correlate with reward-related ventral striatal dopamine release. Journal of Neuroscience. 2008, Vol. 28, 52, pp. 14311-14319.
4. Menon, V and Levitin, DJ. The rewareds of music listening: Response and physiological connectivity of the mesolimbic system. NeuroImage. 2005, Vol. 28, pp. 175-184.
5. Salimpoor, VN., et al. Anatomically distinct dopamine release during anticipation and experience of peak emotion to music. Nature Neuroscience. 2011, Vol. 14, 2, pp. 257-U355.
6. Salimpoor, VN., et al. Interactions between the nucleus accumbens and auditory cortices predict music reward value. Science. 2013, Vol. 340, pp. 216-219.
7. Beranek, L. Concert hall acoustics. J. Acoust. Soc. Am. 1992, Vol. 92, 1, pp. 1-39.
8. Schroeder, MR, Gottlob, D and Siebrasse, KF. Comparative sutdy of European concert halls: correlation of subjective preference with geometric and acoustic parameters. J. Acoust. Soc. Am. 1974, Vol. 56, 4, pp. 1195-1201.
Department of Pediatric Newborn Medicine Brigham and Women’s Hospital Harvard Medical School 75 Francis St Boston, MA 02115
Popular version of 4pAAa12 Are you hearing voices in the high frequencies of human speech and voice? Presented Thursday afternoon, October 30, 2014 168th ASA Meeting, Indianapolis Read the abstract by clicking here.
Ever noticed how or wondered why people sound different on your cell phone than in person? You might already know that the reason is because a cell phone doesn’t transmit all of the sounds that the human voice creates. Specifically, cell phones don’t transmit very low-frequency sounds (below about 300 Hz) or high-frequency sounds (above about 3,400 Hz). The voice can and typically does make sounds at very high frequencies in the “treble” audio range (from about 6,000 Hz up to 20,000 Hz) in the form of vocal overtones and noise from consonants. Your cell phone cuts all of this out, however, leaving it up to your brain to “fill in” if you need it.
Figure 1. A spectrogram showing acoustical energy up to 20,000 Hz (on a logarithmic axis) created by a male human voice. The current cell phone bandwidth (dotted line) only transmits sounds between about 300 and 3400 Hz. High-frequency energy (HFE) above 6000 Hz (solid line) has information potentially useful to the brain when perceiving singing and speech.
What are you missing out on? One way to answer this question is to have individuals listen to only the high frequencies and report what they hear. We can do this using conventional signal processing methods: cut out everything below 6,000 Hz thereby only transmitting sounds above 6,000 Hz to the ear of the listener. When we do this, some listeners only hear chirps and whistles, but most normal-hearing listeners report hearing voices in the high frequencies. Strangely, some voices are very easy to hear out in the high frequencies, while others are quite difficult. The reason for this difference is not yet clear. You might experience this phenomenon if you listen to the following clips of high frequencies from several different voices. (You’ll need a good set of high-fidelity headphones or speakers to ensure you’re getting the high frequencies.)
Until recently, these treble frequencies were only thought to affect some aspects of voice quality or timbre. If you try playing with the treble knob on your sound system you’ll probably notice the change in quality. We now know, however, that it’s more than just quality (see Monson et al., 2014). In fact, the high frequencies carry a surprising amount of information about a vocal sound. For example, could you tell the gender of the voices you heard in the examples? Could you tell whether they were talking or singing? Could you tell what they were saying or singing? (Hint: the words are lyrics to a familiar song.) Most of our listeners could accurately report all of these things, even when we added noise to the recordings.
Figure 2. A frequency spectrum (on a linear axis) showing the energy in the high frequencies combined with speech-shaped low-frequency noise.
What does this all mean? Cell phone and hearing aid technology is now attempting to include transmission of the high frequencies. It is tempting to speculate how inclusion of the high frequencies in cell phones, hearing aids, and even cochlear implants might benefit listeners. Lack of high-frequency information might be why we sometimes experience difficulty understanding someone on our phones, especially when sitting on a noisy bus or at a cocktail party. High frequencies might be of most benefit to children who tend to have better high-frequency hearing than adults. And what about quality? High frequencies certainly play a role in determining voice quality, which means vocalists and sound engineers might want to know the optimal amount of high-frequency energy for the right aesthetic. Some voices naturally produce higher amounts of high-frequency energy, and this might contribute to how well you like that voice. These possibilities give rise to many research questions we hope to pursue in our study of the high frequencies.
REFERENCES
Monson, B. B., Hunter, E. J., Lotto, A. J., and Story, B. H. (2014). “The perceptual significance of high-frequency energy in the human voice,” Frontiers in Psychology, 5, 587, doi: 10.3389/fpsyg.2014.00587.
Transit centered living relies on amenities close to home; mixing multifamily residential units with professional, retail and commercial units on the same site. Use the nearby trains to get to work and out, but rely on the immediate neighborhood, even the lobby for errands and everyday needs. Transit centered living is appealing as it eliminates the need for sitting in traffic, seems good for the environment and adds a sense of security, aerobic health and time-saving convenience. Include an on-site fitness center and residents don’t even have to wear street clothes to get to their gym!
