5aMU1 – The inner ear as a musical instrument

Brian Connolly – bconnolly1987@gmail.com
Music Department
Logic House
South Campus
Maynooth University
Co. Kildare
Ireland

Popular version of paper 5aMU1, “The inner ear as a musical instrument”
Presented Friday morning, November 6, 2015, 8:30 AM, Grand Ballroom 2
170th ASA meeting Jacksonville
See also: The inner ear as a musical instrument – POMA

(please use headphones for listening to all audio samples)

Did you know that your ears could sing? You may be surprised to hear that they, in fact, have the capacity to make particularly good performers and recent psychoacoustics research has revealed the true potential of the ears within musical creativity. ‘Psychoacoustics’ is loosely defined as the study of the perception of sound.

Figure 1: The Ear

inner ear

A good performer can carry out required tasks reliably and without errors. In many respects the very straight-forward nature of the ear’s responses to certain sounds results in the ear proving to be a very reliable performer as its behaviour can be predicted and so it is easily controlled. In the context of the listening system, the inner ear has the ability to behave as a highly effective instrument which can create its own sounds that many experimental musicians have been using to turn the listeners’ ears into participating performers in the realization of their music.

One of the most exciting avenues of musical creativity is the psychoacoustic phenomenon known as otoacoustic emissions. These are tones which are created within the inner ear when it is exposed to certain sounds. One such example of these emissions is ‘difference tones.’ When two clear frequencies enter the ear at, say 1,000Hz and 1,200Hz the listener will hear these two tones, as expected, but the inner ear will also create its own third frequency at 200Hz because this is the mathematical difference between the two original tones. The ear literally sends a 200Hz tone back out in reverse through the ear and this sound can be detected by an in-ear microphone, a process which doctors carrying out hearing tests on babies use as an integral part of their examinations. This means that composers can create certain tones within their work and predict that the listeners’ ears will also add their extra dimension to the music upon hearing it. Within certain loudness and frequency ranges, the listeners will also be able to feel their ears buzzing in response to these stimulus tones! This makes for a very exciting and new layer to contemporary music making and listening.

First listen to this tone. This is very close to the sound your ear will sing back during the second example.

Insert – 200.mp3

Here is the second sample containing just two tones at 1,000Hz and 1,200Hz. See if you can also hear the very low and buzzing difference tone which is not being sent into your ear, it is being created in your ear and sent back out towards your headphones!

Insert – 1000and1200.mp3

If you could hear the 200Hz difference tone in the previous example, have a listen to this much more complex demonstration which will make your ears sing a well known melody. It is important to try to not listen to the louder impulsive sounds and see if you can hear your ears humming along to perform the tune of Twinkle, Twinkle, Little Star at a much lower volume!

(NB: The difference tones will start after about 4 seconds of impulses)

Insert – Twinkle.mp3

Auditory beating is another phenomenon which has caught the interest of many contemporary composers. In the below example you will hear the following: 400Hz in your left ear and 405Hz in your right ear.

First play the below sample by placing the headphones into your ears just one at a time. Not together. You will hear two clear tones when you listen to them separately.

Insert – 400and405beating.mp3

Now try and see what happens when you place them into your ears simultaneously. You will be unable to hear these two tones together. Instead, you will hear a fused tone which beats five times per second. This is because each of your ears are sending electrical signals to the brain telling it what frequency it is responding to but these two frequencies are too close together and so a perceptual confusion occurs resulting in a combined frequency being perceived which beats at a rate which is the same as the mathematical difference between the two tones.

Auditory beating becomes particularly interesting in pieces of music written for surround sound environments when the proximity of the listener to the various speakers plays a key factor and so simply turning one’s head in these scenarios can often entirely change the colour of the sound as different layers of beating will alter the overall timbre of the sound.

So how can all of these be meaningful to composers and listeners alike? The examples shown here are intended to be basic and provide proofs of concept more so than anything else. In the much more complex world of music composition the scope for the employment of such material is seemingly endless. Considering the ear as a musical instrument gives the listener the opportunity to engage with sound and music in a more intimate way than ever before.

Brian Connolly’s compositions which explore such concepts in greater detail can be found at www.soundcloud.com/brianconnolly-1

1pABa2 – Could wind turbine noise interfere with greater prairie chicken (tympanuchus cupido pinnatus) courtship?

Edward J. Walsh – Edward.Walsh@boystown.org
JoAnn McGee – JoAnn.McGee@boystown.org
Boys Town National Research Hospital
555 North 30th St.
Omaha, NE 68131

Cara E. Whalen – carawhalen@gmail.com
Larkin A. Powell – lpowell3@unl.edu
Mary Bomberger Brown – mbrown9@unl.edu
School of Natural Resources
University of Nebraska-Lincoln
Lincoln, NE 68583

Popular version of paper 1pABa2 Hearing sensitivity in the Greater Prairie Chicken
Presented Monday afternoon, May 18, 2015
169th ASA Meeting, Pittsburgh

The Sand Hills ecoregion of central Nebraska is distinguished by rolling grass-stabilized sand dunes that rise up gently from the Ogallala aquifer. The aquifer itself is the source of widely scattered shallow lakes and marshes, some permanent and others that come and go with the seasons.

However, the sheer magnificence of this prairie isn’t its only distinguishing feature. Early on frigid, wind-swept, late-winter mornings, a low pitched hum, interrupted by the occasional dawn song of a Western Meadowlark (Sturnella neglecta) and other songbirds inhabiting the region, is virtually impossible to ignore.

Click here to listen to the hum

The hum is the chorus of the Greater Prairie Chicken (Tympanuchus cupido pinnatus), the communal expression of the courtship song of lekking male birds performing an elaborate testosterone-driven, foot-pounding ballet that will decide which males are selected to pass genes to the next generation; the word “lek” is the name of the so-called “booming” or courtship grounds where the birds perform their wooing displays.

While the birds cackle, whine, and whoop to defend territories and attract mates, it is the loud “booming” call, an integral component of the courtship display that attracts the interest of the bioacoustician – and the female prairie chicken.

The “boom” is an utterance that is carried long distances over the rolling grasslands and wetlands by a narrow band of frequencies ranging from roughly 270 to 325 cycles per second (Whalen et al., 2014). It lasts about 1.9 seconds and is repeated frequently throughout the morning courtship ritual.
Usually, the display begins with a brief but energetic bout of foot stamping or dancing, which is followed by an audible tail flap that gives way to the “boom” itself.

Watch the video clip below to observe the courtship display

For the more acoustically and technologically inclined, a graphic representation of the pressure wave of a “boom,” along with its spectrogram (a visual representation showing how the frequency content of the call changes during the course of the bout) and graphs depicting precisely where in the spectral domain the bulk of the acoustic power is carried is shown in Figure 1. The “boom” is clearly dominated by very low frequencies that are centered on approximately 300 Hz (cycles per second).

FIGURE 1 (file missing): Acoustics Characteristics of the “BOOM”

Vocalization is, of course, only one side of the communication equation. Knowing what these stunning birds can hear is on the other. We are interested in what Greater Prairie Chickens can hear because wind energy developments are encroaching onto their habitat, a condition that makes us question whether noise generated by wind turbines might have the capacity to mask vocal output and complicate communication between “booming” males and attending females.

Step number one in addressing this question is to determine what sounds the birds are capable of hearing – what their active auditory space looks like. The golden standard of hearing tests are behavioral in nature – you know, the ‘raise your hand or press this button if you can hear this sound’ kind of testing. However, this method isn’t very practical in a field setting; you can’t easily ask a Greater Prairie Chicken to raise its hand, or in this case its wing, when it hears the target sound.

To solve this problem, we turn to electrophysiology – to an evoked brain potential that is a measure of the electrical activity produced by the auditory parts of the inner ear and brain in response to sound. The specific test that we settled on is known as the ABR, the auditory brainstem response.

The ABR is a fairly remarkable response that captures much of the peripheral and central auditory pathway in action when short tone bursts are delivered to the animal. Within approximately 5 milliseconds following the presentation of a stimulus, the auditory periphery and brain produce a series of as many as five positive-going, highly reproducible electrical waves. These waves, or voltage peaks, more or less represent the sequential activation of primary auditory centers sweeping from the auditory nerve (the VIIIth cranial nerve), which transmits the responses of the sensory cells of the inner ear rostrally, through auditory brainstem centers toward the auditory cortex.

Greater Prairie Chickens included in this study were captured using nets that were placed on leks in the early morning hours. Captured birds were transported to a storage building that had been reconfigured into a remote auditory physiology lab where ABRs were recorded from birds positioned in a homemade, sound attenuating space – an acoustic wedge-lined wooden box.

FIGURE 2 (file missing): ABR Waveforms

The waveform of the Greater Prairie Chicken ABR closely resembles ABRs recorded from other birds – three prominent positive-going electrical peaks, and two smaller amplitude waves that follow, are easily identified, especially at higher levels of stimulation. In Figure 2, ABR waveforms recorded from an individual bird in response to 2.8 kHz tone pips are shown in the left panel and the group averages of all birds studied under the same stimulus conditions are shown in the right panel; the similarity of response waveforms from bird to bird, as indicated in the nearly imperceptible standard errors (shown in gray), testifies to the stability and utility of the tool. As stimulus level is lowered, ABR peaks decrease in amplitude and occur at later time points following stimulus onset.

Since our goal was to determine if Greater Prairie Chickens are sensitive to sounds produced by wind turbines, we generated an audiogram based on level-dependent changes in ABRs representing responses to tone pips spanning much of the bird’s audiometric range (Figure 3). An audiogram is a curve representing the relationship between response threshold (i.e., the lowest stimulus level producing a clear response) and stimulus frequency; in this case, thresholds were averaged across all animals included in the investigation.

FIGURE 3 (file missing): Audiogram and wind turbine noise

As shown in Figure 3, the region of greatest hearing sensitivity is in the 1 to 4 kHz range and thresholds increase (sensitivity is lost) rapidly at higher stimulus frequencies and more gradually at lower frequencies. Others have shown that ABR threshold values are approximately 30 dB higher than thresholds determined behaviorally in the budgerigar (Melopsittacus undulates) (Brittan-Powell et al., 2002). So, to answer the question posed in this investigation, ABR threshold values were adjusted to estimate behavioral thresholds, and the resulting sensitivity curve was compared with the acoustic output of a wind turbine farm studied by van den Berg in 2006. The finding is clear; wind turbine noise falls well within the audible space of Greater Prairie Chickens occupying booming grounds in the acoustic footprint of active wind turbines.

While findings reported here indicate that Greater Prairie Chickens are sensitive to at least a portion of wind turbine acoustic output, the next question that we plan to address will be more difficult to answer: Does noise propagated from wind turbines interfere with vocal communication among Greater Prairie Chickens courting one another in the Nebraska Sand Hills? Efforts to answer that question are in the works.

tags: chickens, mating, courtship, hearing, Nebraska, wind turbines

References
Brittan-Powell, E.F., Dooling, R.J. and Gleich, O. (2002). Auditory brainstem responses in adult budgerigars (Melopsittacus undulates). J. Acoust. Soc. Am. 112:999-1008.
van den Berg, G.P. (2006). The sound of high winds. The effect of atmospheric stability on wind turbine sound and microphone noise. Dissertation, Groningen University, Groningen, The Netherlands.
Whalen, C., Brown, M.B., McGee, J., Powell, L.A., Smith, J.A. and Walsh, E.J. (2014). The acoustic characteristics of greater prairie-chicken vocalizations. J. Acoust. Soc. Am. 136:2073.

1pSC2 – Deciding to go (or not to go) to the party may depend as much on your memory as on your hearing

Kathy Pichora-Fuller – k.pichora.fuller@utoronto.ca
Department of Psychology, University of Toronto,
3359 Mississauga Road,
Mississauga, Ontario, CANADA L5L 1C6

Sherri Smith – Sherri.Smith@va.gov
Audiologic Rehabilitation Laboratory, Veterans Affairs Medical Center,
Mountain Home, Tennessee, UNITED STATES 37684

Popular version of paper 1pSC2 Effects of age, hearing loss and linguistic complexity on listening effort as measured by working memory span
Presented Monday afternoon, May 18, 2015 (Session: Listening Effort II)
169th ASA Meeting, Pittsburgh

Understanding conversation in noisy everyday situations can be a challenge for listeners, especially individuals who are older and/or hard-of-hearing. Listening in some everyday situations (e.g., at dinner parties) can be so challenging that people might even decide that they would rather stay home than go out. Eventually, avoiding these situations can damage relationships with family and friends and reduce enjoyment of and participation in activities. What are the reasons for these difficulties and why are some people affected more than other people?

How easy or challenging it is to listen may vary from person to person because some people have better hearing abilities and/or cognitive abilities compared to other people. The hearing abilities of some people may be affected by the degree or type of their hearing loss. The cognitive abilities of some people, for example how well they can attend to and remember what they have heard, can also affect how easy it is for them to follow conversation in challenging listening situations. In addition to hearing abilities, cognitive abilities seem to be particularly relevant because in many everyday listening situations people need to listen to more than one person talking at the same time and/or they may need to listen while doing something else such as driving a car or crossing a busy street. The auditory demands that a listener faces in a situation increase as background noise becomes louder or as more interfering sounds combine with each other. The cognitive demands in a situation increase when listeners need to keep track of more people talking or to divide their attention as they try to do more tasks at the same time. Both auditory and cognitive demands could result in the situation becoming very challenging and these demands may even totally overload a listener.

One way to measure information overload is to see how much a person remembers after they have completed a set of tasks. For several decades, cognitive psychologists have been interested in ‘working memory’, or a person’s limited capacity to process information while doing tasks and to remember information after the tasks have been completed. Like a bank account, the more cognitive capacity is spent on processing information while doing tasks, the less cognitive capacity will remain available for remembering and using the information later. Importantly, some people have bigger working memories than other people and people who have a bigger working memory are usually better at understanding written and spoken language. Indeed, many researchers have measured working memory span for reading (i.e., a task involving the processing and recall of visual information) to minimize ‘contamination’ from the effects of hearing loss that might be a problem if they measured working memory span for listening. However, variations in difficulty due to hearing loss may be critically important in assessing how the demands of listening affect different individuals when they are trying to understand speech in noise. Some researchers have studied the effects of the acoustical properties of speech and interfering noises on listening, but less is known about how variations in the type of language materials (words, sentences, stories) might alter listening demands for people who have hearing loss. Therefore, to learn more about why some people cope better when listening to conversation in noise, we need to discover how both their auditory and their cognitive abilities come into play during everyday listening for a range of spoken materials.

We predicted that speech understanding would be more highly associated with working memory span for listening than with listening span for reading, especially when more realistic language materials are used to measure speech understanding. To test these predictions, we conducted listening and reading tests of working memory and we also measured memory abilities using five other measures (three auditory memory tests and two visual memory tests). Speech understanding was measured with six tests (two tests with words, one in quiet and one in noise; three tests with sentences, one in quiet and two in noise; one test with stories in quiet). The tests of speech understanding using words and sentences were selected from typical clinical tests and involved simple immediate repetition of the words or sentences that were heard. The test using stories has been used in laboratory research and involved comprehension questions after the end of the story. Three groups with 24 people in each group were tested: one group of younger adults (mean age = 23.5 years) with normal hearing and two groups of older adults with hearing loss (one group with mean age = 66.3 years and the other group with mean age 74.3 years).

There was a wide range in performance on the listening test of working memory, but performance on the reading test of working memory was more limited and poorer. Overall, there was a significant correlation between the results on the reading and listening working memory measures. However, when correlations were conducted for each of the three groups separately, the correlation reached significance only for the oldest listeners with hearing loss; this group had lower mean scores on both tests. Surprisingly, for all three groups, there were no significant correlations among the working memory and speech understanding measures. To further investigate this surprising result, a factor analysis was conducted. The results of the factor analysis suggest that there was one factor including age, hearing test results and performance on speech understanding measures when the speech-understanding task was simply to repeat words or sentences – these seem to reflect auditory abilities. In addition, separate factors were found for performance on the speech understanding measures involving the comprehension of discourse or the use of semantic context in sentences – these seem to reflect linguistic abilities. Importantly, the majority of the memory measures were distinct from both kinds of speech understanding measures, and also a more basic and less cognitively demanding memory measure involving only the repetition of sets of numbers. Taken together, these findings suggest that working memory measures reflect differences between people in cognitive abilities that are distinct from those tapped by the sorts of simple measures of hearing and speech understanding that have been used in the clinic. Above and beyond current clinical tests, by testing working memory, especially listening working memory, useful information could be gained about why some people cope better than others in everyday challenging listening situations.

tags: age, hearing, memory, linguistics, speech