The acoustics of rooms for music rehearsal and performance – The Norwegian approach – Jon G. Olsen

The acoustics of rooms for music rehearsal and performance – The Norwegian approach – Jon G. Olsen

The acoustics of rooms for music rehearsal and performance – The Norwegian approach

Jon G. Olsen –

Council for Music Organizations in Norway, Oslo, Norway


Jens Holger Rindel –

Multiconsult, Oslo, Norway


Popular version of paper 2pAAb1, “The acoustics of rooms for music rehearsal and performance – the Norwegian approach”

Presented Monday afternoon, June 26, 2017, 1:20 pm.

173rd ASA Meeting / 8th Forum Acusticum, Boston, USA


Each week, local music groups in Norway use more than 10,000 rooms for rehearsals and concerts. Over 500,000 people sing, play or go to concerts every week. In Europe, over 40 million choir singers spend at least one evening in a rehearsal room. Professional musicians and singers use rehearsal rooms many hours a day. Most of the local concerts take place in rooms that are not designed for concert events, but are in schools, community centers, youth clubs and other rooms and spaces more or less suitable for playing music.

The size of the rooms varies from under 100 to over 10, 000 cubic meters. The users cover a broad variety of music ensembles, mostly wind bands, choirs and other amateur ensembles. Since 2009, the Norwegian Council for Music Organizations (Norsk musikkråd) has completed more than 600 acoustical room measurement reports on rooms used for rehearsal and concerts. All the reports are made available online with a Google Map of Norway (

The results are depressing: 85 % of the rooms are not suited for the type of music for which they are used. A faulty type of acoustics can enforce the music ensemble to adapt to wrong balance between the instruments, making the musical interaction much more difficult and reducing the possibility for developing a good sound – both for each musician and for the orchestra or choir as a whole.

Unsuitable acoustics reduce the musical quality of the music group and give the conductor less possibility to work with and develop the musical quality. It also reduces the joy of playing or singing in a local music group. As the famous conductor Mariss Janssons used to say, “A good hall for the orchestra is as important as a good instrument is for a soloist.”

Different types of music need different types of rooms and different acoustical conditions. We can divide the music genres into three main groups:

  • Acoustically soft music, such as singing and playing instruments that are relatively quiet, such as string instruments, guitars etc. and smaller woodwind ensembles.
  • Acoustically loud music, such as playing brass instruments and percussion instruments, brass bands, concert bands, symphony orchestras and opera singing.
  • Amplified music, such as pop/rock bands, amplified jazz groups etc.

The Norwegian Standardization Organization established a working group, with participants from the Council for Music Organizations in Norway, the music industry, municipalities, acoustic consultants, The Union of Norwegian Musicians and others. Together, this group has developed the National standard, “Acoustic criteria for rooms and spaces for music rehearsal and performance” NS 8178:2014.

The Norwegian standardization group has divided rooms into five categories and provided specific requirements for each:

  • Individual practice room (1-2 musicians practicing)
  • Small ensemble room (3-6 musicians, teaching rooms)
  • Medium size ensemble room (up to 20 musicians/singers)
  • Large ensemble room (for choir, school band, concert band, symphonic band with brass/percussion, acoustic big band)
  • Performance rooms, subdivided into four types of rooms
    • Amplified music club scenes (small jazz, pop, singer/songwriter)
    • Amplified music concert rooms (pop/rock/jazz/blues)
    • Acoustic loud music (concert band, symphony orchestra, brass band, big band)
    • Acoustic quiet music (vocal group, string orchestra, folk music group, chamber music)

VOLUME – the most important criterion

Too small a volume turns out to be the main problem for many ensembles. A survey of Norwegian choir rehearsal rooms shows that 54% of the rooms are excessively small (less than half the size they should have been), 22% are too small and only 24% have more or less enough volume.

Figure 1.: Query Norwegian singer’s organization, spring 2016. Rehearsal room size.

For wind bands, we see more or less the same situation where the rooms are in general too small. In music schools, there are also many studios that are too small. The result is that the music is far too loud, and it is very difficult to work with sound quality and dynamic expression.

ROOM GEOMETRY – criterion number 2

This criterion poses not so many problems, apart from the fact that the room height is often too small, particularly in rehearsal rooms, but also in a number of concert rooms. A low ceiling is bad for the sound quality of the instruments and makes it difficult to hear each other.

REVERBRATION TIME – criterion number 3

There are often problems with the reverberation time, different for each of the three types of music. For acoustic soft music, the reverberation time should be relatively long in order to give support to the music, but it is very often too short in rehearsal and concert rooms. For acoustic loud music, the reverberation time should be moderate in order to avoid the music to be too loud, but it is often too long – or sometimes too short.

For amplified music, the reverberation time should be short, and this is quite often the case. However, it is especially important to have sufficiently short reverberation time in the bass (the low frequencies); otherwise the music makes an unpleasant booming sound.

The Norwegian standard provides a basis for better design of new music rooms. The systematic collection of acoustic reports of music rooms gives important background for recommendations on how to build or refurbish rooms for music in schools and cultural buildings.

Picture 1: Brass band rehearsal at Toneheim college, Norway,
Credit: Trond Eklund Johansen, Hedmark/Oppland Music Council

A Loud, Ultrasonic Party – Yanqing Fu

A Loud, Ultrasonic Party – Yanqing Fu

A Loud, Ultrasonic Party

Quantifying complex bat calls to understand how bats echolocate in groups

Contact: Yanqing Fu,


Yanqing Fu, Laura N. Kloepper

Department of Biology, Saint Mary’s College,

Notre Dame, IN 46556


Popular version of paper 2aAB3, “First harmonic shape analysis of Brazilian free-tailed bat calls during emergence.”

Presented Monday morning, June 26, 2017

173rdASA Meeting, Boston


Imagine you are at a party. The music is loud and lots of people are talking. How can you hear your voice and those of other people? Similarly, bats face this problem when in groups. When a single bat uses echolocation, it emits an ultrasonic call (above 20 kHz) and extracts environmental information by analyzing echoes.


But for bats that live and travel in large groups, echolocation should be challenging. Under these circumstances, they should encounter the problem of sonar jamming, where they might have a hard time distinguishing their echoes from other bats’ and their own calls. One bat species that is known for extreme grouping is the Brazilian free-tailed bat, Tadarida brasiliensis.


Figure 1: Brazilian free-tailed bat (Tadarida brasiliensis) emergence, which usually occurs from 16:00 to 20:00, last about 15 minutes.


These bats can quickly change characteristics of their calls when probing different environments and performing different tasks. These call characteristics include duration, repetition rate, and frequency (or pitch). The shape of a call, how the call changes frequency over time, may provide important echo information to the bat.


Brazilian free-tailed bats can change the call shape from a straight line (constant frequency) to a downward curved line (nonlinear frequency modulation) and finally an inclined line (linear frequency modulation) within milliseconds (Fig. 2). Additionally, the bats can emit different frequency components at the same time. The call shape variation of bats flying in a group might help us to understand how they avoid sonar jamming.


Figure 2: Typical call shapes of Brazilian free-tailed bat (Tadarida brasiliensis).


In order to investigate how these bats change calls while flying in groups, we developed a new method to identify the shape of a bat call and quantitatively compare different call shapes. This method separates the multiple frequency components of bat calls (called harmonics) and tracks the trend of frequency over time using advanced digital signal processing techniques (Fig. 3).


Once these trends are extracted, call shapes can be quantitatively compared through point-to-point comparison by aligning different call durations. This method is the first important step to understanding how bats avoid sonar jamming while in large groups. We hypothesize that some call shapes are more robust to distinguish than others when in a chaotic sound environment.


Figure 3:  Typical procedures for the isolation and tracking the first frequency component of the Brazilian free-tailed bat echolocation call. (a) Original echolocation call; (b) low frequency noise free call; (c) noise among different frequency components was removed; (d) isolated clean first frequency component; (e) call shape was extracted, black solid line superimposed on the isolated frequency component.


How Canaries Listen to Their Song – Adam R. Fishbein

How Canaries Listen to Their Song – Adam R. Fishbein

How Canaries Listen to Their Song

Adam R. Fishbein –

Shelby L. Lawson

Gregory F. Ball

Robert J. Dooling

University of Maryland

4123 Biology-Psychology Building

College Park, MD 20742


Popular version of paper 3pAB5

Presented Tuesday afternoon, June 27, 2017

173rd ASA Meeting, Boston


The melodic, rolling songs of canaries have entertained humans for centuries. But for canaries, these songs play an important role in courtship. The song, produced exclusively by males, can last for minutes and consists of various syllables repeated in flexibly sequenced phrases.


Earlier behavioral observations have shown that females are especially attracted to so-called “sexy” syllables or “sexy” phrases. These are characterized by a fast tempo, wide-bandwidth (meaning that they extend from low to high pitch), and a two-note structure. Researchers have argued that females have evolved to prefer these syllables because they are difficult to produce and thus provide an honest signal of the male’s quality [1][2]. That is, sexy syllables indicate a strong, healthy male with good genes.



Figure 1 Recording of canary song (left)

and spectrogram of “sexy” phrase (right).


The two red lines indicate the two notes of the sexy syllable. (Credit: Fishbein)


We explored how canaries in a non-breeding state (i.e. short days) listen to their song by testing their auditory perception using the equivalent of a human hearing test. Since the birds can’t tell us “yes” or “no” when asked if two sounds are different, we train them to listen to a repeating sound and peck a key when the sound changes. If they respond correctly, this tells us they can hear the difference between the sounds and they are then rewarded with brief access to food.


Figure 2 Canary in testing chamber. (Credit: Fishbein)

Some of the questions we posed are: Do sexy phrases sound different to canaries than other phrases? Do they listen more to the fine details of every syllable or to the overall flow of the song? Are females more sensitive to “sexy” qualities than males? Do other birds hear canary song differently than canaries?

In one experiment, we asked canaries to distinguish between eight different song phrases: four “sexy” ones and four “non-sexy” ones. We analyzed the birds’ responses and created a “perceptual map” that visually represents how distinct the phrases sound to the canaries.

Our results show that canaries perceive a bird’s sexy phrases as more similar to each other than other phrases, confirming that canaries find these sexy syllable vocalizations particularly salient.


Figure 3 “Perceptual map” for canaries. Circles indicate phrases taken from recordings of bird A. Diamonds indicate phrases taken from recordings of bird B. Blue labels are non-sexy phrases and red ones are sexy. Axis labels indicate the acoustic features that each dimension correlates with. (Credit: Fishbein)

Other experiments in this study provided further evidence that sexy song syllables sound distinctive to canaries. Canaries could hear synthesized reversals of sexy syllables, but performed better at reversals of non-sexy ones. They were also better at hearing increases in the tempo of sexy syllables than decreases in tempo. These results suggested that canaries may be attuned to perceiving the fast tempo and coordinated notes of the sexy syllables. Importantly, these findings were the case for both female and male canaries, perhaps because male canaries need to assess competitors and maintain their own song, just as females need to find the highest quality mate.

Canaries are not exceptional in being able to hear the fine details of their song. Other species tested with these song manipulations are similarly sensitive to small temporal differences between notes in sexy syllables.

Taken together, these results suggest that canaries listen to chunk by chunk, phrase by phrase changes in their song, keying in to details about sexiness when those particular syllables occur. In the future, it will be interesting to compare these perceptual results from canaries in a non-breeding state to canaries that are on long days, with elevated hormone levels, preparing to breed.

In a way, canaries seem to listen to song like we listen to an orchestral symphony, hearing the melody and rhythm of the whole piece, integrating the contributions of each instrument, and not zooming in on the performance of a single instrument except during an especially impressive solo.



  1. Vallet, E., Kreutzer, M., 1995. “Female canaries are sexually responsive to special song phrases.” Animal Behavior. 49, 1603-1610.
  2. Suthers, R., Vallet, E., Kreutzer, M., 2012. “Bilateral coordination and the motor basis of female preference for sexual signals in canary song.” Journal of Experimental Biology. 215, 2950-2959.




My personal head related transfer function – Sebastián Fingerhuth 

My personal head related transfer function – Sebastián Fingerhuth 

My personal head related transfer function

High quality individualized computer models


Sebastián Fingerhuth

Danny Angles      

Juan Barraza       

School of Electrical Engineering

Pontificia Universidad Católica de Valparaíso

Av. Brasil 2147 – Valparaíso – Chile.


Our ability to precisely locate where a sound comes from is due to many factors, noteably that we have two ears and our brains can use the geometry of our head and ears to distinguish originating direction. The fact we hear with two ears is called binaural hearing. It has been a matter of study and research for many years and has many technological applications.

Among the outstanding applications are: 3D sound reproduction and recording systems, architectural acoustic designs, sound design, individualized adjustments of orthopedic hearing aids, teleconferencing systems, among others.

Hardware equipment called dummy heads allow us to study this topic [3] [4]. They are available purchase and at some research institutions and consist of a real-sized artificial head, including two ears that have microphones in the ear channels. With a dummy head, it is possible to record sound exactly as if it were on our own ears. This has led to the production of some of the amazing 3D recording available for computer games, videos, and other music production. These dummy heads are also used intensively for research purposes.

There is an ITU (International Telecommunications Union) standard for dummy heads, but it is hardly sufficient to fully model individual heads, likely representing only average head dimensions, or median sizes. My individual head is different to a dummy head and these differences, in size and geometry, can affect how good or accurate the results of auditory measurements can be.

The innovation of our research is in the development of a methodology constructing individual 3D computer models (CAD) of heads and ears, including the outer part of the ear, called the pinna. The results of these three-dimensional models can be used to directly compute individual acoustics parameters on a computer or to build an individual dummy head.


Video: Model 3D CAD (Credit: Fingerhuth/Angles/ Barraza)


The methodology to obtain the 3D CAD models has to steps: i) the model of the head and ii) the 3D replicas of the ear.

Model of the head

Photogrammetry is a method used to get 3-D information from a set of pictures taken of the object of interest, such as a head. If we want a high resolution and high precision model of the head, we need many pictures, from different angles and positions, to cover the head fully. We use the processing software 3D Zephy, but there other options exist. Finally, we obtain a 3D CAD model which also includes the color and texture of the object, but only the geometry is of interest for acoustics.

Figure 1. Upper Images: Control points marked on the persons face before the photo session. (Credit: Fingerhuth/Angles/ Barraza) Lower Images: 3D CAD model (with and without texture) including control distances measured with the software (Credit: Fingerhuth/Angles/ Barraza)

Ear Replicas

The form and geometry of the pinna makes it almost impossible to get an accurate 3D CAD model from a pure photogrammetry method. Therefore, we used a molding process [5] [6]. First an alginate negative is created and then a plaster positive. Most of the plaster pinnae are cut, to open and show the concavities (Figure 2).

Figure 2. Plaster replicas of the pinna. The original one, from a dummy head on the left. (Credit: Fingerhuth/Angles/ Barraza)


3D Scanner

The plaster models of the pinna can be converted in a 3D CAD model using photogrammetry again or by means of a 3D scanner. We used the latter, and the result is shown in Figure 3. This method uses a combination of laser and imaging on a small rotating platform.

Figure 3. Scanning process of the pinna. In this case, a standard pinna from a commercial dummy head. (Credit: Fingerhuth/Angles/ Barraza)



We tested and compared the results of each one of these processes (e.g. See control points and distances on the participants and on the CAD model in Figure 1). To check how robust the methods are, we also performed additional quality tests: We used more or fewer pictures in the photogrammetry software, photo-sessions for the same participant were repeated on different days, etc.

The results of these comparison showed us that the mean error was lower than 1.5%. Finally, the partial results, consisting of one CAD model of the head and two CAD pinnae, were joined to form one 3D CAD model (Figure 4) that will be used to compute the acoustic cues for that specific person (this is called the Head Related Transfer Function, HRTF).

We will compare our results in its quality with 3D audio localization listening test with that same participant. This will finally give information about how good this hybrid process is for obtaining individualized dummy heads.

Figure 4. Result from the hybrid model obtaining process. (Credit: Fingerhuth/Angles/ Barraza)



[1] D. Batteau, «The role of the Pinna in Human Localization,» Proceeding of The Royal Society Biological Sciences, vol. 168, pp. 158-180, 1967.
[2] J. S. Rayleigh, The Theory of Sound, London: Macmillan, 1877.
[3] K. Martin y G. Bill, «HRTF Measurements of a KEMAR Dummy-Head Microphone,» MIT Media Lab, Massachuset, 1994.
[4] F. Wightman y D. Kistler, «Headphone simulation of free-field listening. I: Stimulus synthesis,» The Journal of the Acoustical Society of America, vol. 85, nº 2, p. 858, 1998.
[5] J. L. Bravo , «Construcción de Modelo de Oreja Artificial de Silicona y Medición de Características Acústicas,» Valparaíso, 2015.
[6] R. Codoceo, «Construcción de Modelos 3D de Oreja y Cabeza Individualizada para Medición Acústica,» Valparaíso, 2016.






S&N-S Light: the system that makes the noise light – Sonja Di Blasio

S&N-S Light: the system that makes the noise light – Sonja Di Blasio

S&N-S Light: the system that makes the noise light

Sonja Di Blasio–
Giuseppina Emma Puglisi–
Giuseppe Vannelli –
Louena Shtrepi–
Marco Carlo Masoero –
Arianna Astolfi–

Dipartimento di Energia
Politecnico di Torino
Corso Duca degli Abruzzi, 24
10129 Torino

Simone Corbellini –
Dipartimento di Elettronica e Telecomunicazioni
Politecnico di Torino
Corso Duca degli Abruzzi, 24
10129 Torino

In collaboration with:
Giulia Calosso –
Alessia Griginis –
Via Antonio Pigafetta, 3
10129 Torino
Stefano Cerruti –
BSA – Bottega Studio Architetti
Via degli Stampatori, 4
10128 Torino

Black logo of S&N-S Light Credit:ONLECO S.r.l


Recently, the tendency in many fields related to environmental quality, such as thermal and visual quality, is to customise the comfort according to users’ needs. A tailored comfort zone is planned for public spaces, in which occupants can set their own comfort level with passive or active systems. In this context, the reduction of noise due to anthropic sources is a priority.

In densely occupied spaces, such as classrooms, workplaces, restaurants and outdoor spaces, the noise due to other people chatting has a detrimental effect upon performance, health and environmental quality. In these spaces, the way to reduce noise is usually based on the acoustic refurbishment of the rooms, in terms of sound absorption and sound insulation [1].

Strategies able to involve the users actively to obtain good acoustic quality have not yet been largely developed. Since high noise levels due to people chatting have been defined as the main source of acoustic pollution in these spaces [2,3,4], focusing on the occupant behaviour can be an effective strategy to obtain acoustic comfort through active role of the users.

We developed Speech & Noise-Stop Light, S&N-S Light, a patented, smart sound level meter device with a warning light triggered by exceeding a predetermined anthropic sound level difference, which encourages personal voice control through visual feedback. The light activation, with green, yellow and red colour, is based on an adaptive algorithm that filters accidental noise levels.

The main aims of S&N-S Light are: To increase social awareness about noise impact on health and comfort; and to encourage people toward personal voice control to reduce anthropic noise levels and obtain acoustic comfort through an active social behaviour.

Its prototype is a transparent panel illuminated by a through‐light colour beam (see Figure 1). It is largely used to control chatting noise in classrooms, and therefore applied as educational tool.


Figure 1 – Example of application of S&N-S Light in a classroom of the primary school “Roberto d’Azeglio” in Torino during a measurement campaign. Credit: Sonja/POLITO

The innovation is in the adaptive algorithm, which makes S&N-S Light different from competitors (see Figure 2). The light activation is based on a time history, thus allowing S&N-S Light to automatically adapt to the changes in the noise conditions.

In this way, it considers the fact that people can also be annoyed in the case of low noise levels, like when the noise increases compared to a previous condition, especially in the case of cognitive tasks. Moreover, S&N-S Light is also able to filter the noise due to accidental events, such as a teacher’s shout or a sneeze.

Figure 2 – Innovative elements that charaterize S&N-S Light.* Credit: Sonja/POLITO and Creative Common licence (

Six prototypes have been produced so far and successfully applied in primary and secondary school classrooms. The architecture is shown in Figure 3. A class-2, low-cost sound level meter records noise levels at a fixed time interval, and an electronic card processes the signals and activates the warning light which lights up the transparent panel. A Wi-Fi module has been added to send data to a cloud server platform and on a customised mobile App in real time. The future aim is to design a new device to extend application of S&N-S Light to open-plan offices and restaurants.

Figure 3 – Architecture of the S&N-S Light prototype and screenshot of the mobile App. Credit: Sonja/Simone/POLITO

We carried out several measurement campaigns in classrooms of different type of schools. Results highlighted a statistically significant decrease in noise levels, as shown in Figure 4 and Table I, especially in the first week in which S&N-S Light is switched on.


Figure 4 – Example of occurrences distribution of L90 in a primary school classroom with S&N-S Light switched off and switched on. It can be shown that the most occurrent value decreased by about 8 dB. Credit: Sonja/POLITO


Table I – L90 reduction with S&N-S Light switched on in four primary school classes. The reliability of the improvements has been based on the the Mann‐Whitney U Test,  a non parametric statistical test that it used to interpret whether there are differences in the occurrences distributions of two groups.

The experiments in the classrooms demonstrated a noise level decrease with S&N-S Light switched on (week 1 and week 2) compared to S&N-S Light switched off (week 0). Furthermore, the decrease in noise level results higher in week 1 compared to week 2. Currently, we are organizing a further measurement campaign in a primary school to investigate whether training for children, repeated each week, could reduce the difference between week 1 and week 2.


[1] Kristiansen J., Lund S.P., Persson R., Challi R., Lindskov J. M., Nielsen P.M., Larsen P.K., Toftum J., The effects of acoustical refurbishment of classrooms on teachers’ perceived noise exposure and noise-related health symptoms, International Archives of Occupational and Environment Heath, 89 (2016), pp. 341-350.


[2] Astolfi A., Pellerey F., Subjective and objective assessment of acoustical and overall environmental quality in secondary school classrooms, Journal of the Acoustical Society of America, 123(1) (2008), pp. 163-173.


[3] Dockrell J. E., Shield B., Children’s perceptions of their acoustical environment at school and at home, Journal of the Acoustical Society of America, 115 (6) (2004), pp. 2964-2973.


[4] Ottoz E., Rizzi L., Nastasi F., Recreational noise in Turin and Milan: impact and costs of movida for disturbed residents, In: Proceedings of the 22th International Congress on Sound and Vibration, (2008), pp. 1-8.


* Terms of Use: These icons are licensed under a Creative Commons Attribution 3.0 United States (CC BY 3.0 US ( They are attributed to Nurfakeh Fuji Amaludin, Pascual Bilotta, Magicon and Becris, and the original version can be found here