5pAAa4 – The clapping circle “squeak,” finally explained – Elspeth Wing

“The clapping circle “squeak,” finally explained”


Elspeth Wing – winge@purdue.edu

Steven Herr – sherr@purdue.edu

Alexander Petty – petty14@purdue.edu

Alexander Dufour – adufour@purdue.edu

Frederick Hoham – fhoham@purdue.edu

Morgan Merrill – mmerril@purdue.edu

Donovan Samphier – dsamphie@purdue.edu

Weimin Thor – wthor@purdue.edu

Kushagra Singh – singh500@purdue.edu

Yutong Xue – xyt@alumni.purdue.edu

Davin Huston – dhhustion@purdue.edu

Stuart Bolton – bolton@purdue.edu

Purdue University

610 Purdue Mall

West Lafayette, IN 47907


Popular version of paper 5pAAa4 (your paper version)

Presented Friday morning, December 11, 2020

179th ASA Meeting, Acoustics Virtually Everywhere


Ask any member of the Purdue University community about the “Clapping Circle,” and they will eagerly tell you about the unforgettable squeak that appears to materialize out of thin air when you stand in the middle of it and clap your hands. In 2019, the Purdue student chapter of the Acoustical Society of America gathered a team of undergraduate students, graduate students, and faculty to conduct a study to establish, once and for all, the specific acoustic mechanisms behind “the squeak.”

An aerial photo of the Clapping Circle

A recording of the clap and subsequent squeak


The Clapping Circle is a circular plaza consisting of sixty-six concentric rings of stone tiles, and with stone benches on its edges. This architectural feature has led to numerous theories from acoustics experts about the cause: from reflections off the ground tiles, to the surrounding benches, or even the surrounding trees and buildings.


The members of the Purdue student chapter of the ASA decided to thoroughly investigate. They set up a multidirectional speaker in the middle to simulate a clap at different heights, and then recorded the results through a microphone. They even covered the entire circle in moving blankets to act as a control.

A photograph of the speaker and microphone in the middle of the circle during testing


The experiments confirmed their theory: two phenomena known as “acoustical diffraction grating” and “repetition pitch”  combined to create the effect.  Acoustical diffraction grating refers to the reinforcement of certain frequencies produced by a reflection, which they theorized was coming from the progressively more distant bevels between the ground tiles. “Repetition pitch” refers to the ear’s processing of repeated percussive sounds as a pitch. Put both of these together, and you get a rapidly descending pitch which sounds like a squeak.


When they covered the circle with hundreds of moving blankets, the squeak disappeared – ultimately proving their theory correct.


While similar studies have been performed at stepped architectural features (such as the pyramid at Chichen-Itza), this is the most completely researched explanation of the “clapping circle” phenomenon.  And now, thanks to these diligent acoustics students, the tour guides at Purdue University will have a proper scientific explanation for “the squeak!”

Some of the investigation team at the site

the video link below, Link to a promotional video about the project created by Purdue University

More information: https://www.purdue.edu/newsroom/stories/2020/Stories%20at%20Purdue/explaining-the-sound-of-purdues-clapping-circle.html


Video: https://www.youtube.com/watch?v=Cuv1Pd_hS_I

1aSC3 – Acoustic changes of speech during the later years of life – Benjamin Tucker

Acoustic changes of speech during the later years of life

Benjamin Tucker – benjamin.tucker@ualberta.ca

Stephanie Hedges – shedges@ualberta.ca

Department of Linguistics

University of Alberta

Edmonton, Alberta T6G 2E7



Mark Berardi – mberardi@msu.edu

Eric Hunter – ejhunter@msu.edu

Department of Communicative Sciences and Disorders
Michigan State University
East Lansing, Michigan 48824


Popular version of paper 1aSC3 (your paper version)

Presented Monday morning 11:15 AM – 12:00P PM, December 7, 2020

179th ASA Meeting, Acoustics Virtually Everywhere


Research into the perception and production of the human voice has shown that the human voice changes with age (e.g., Harnsberger et al., 2008). Most of the previous studies have investigated speech changes over time using groups of people of different ages, while a few studies have tracked how an individual speaker’s voice changes over time. The present study investigates three male speakers and how their voices change over the last 30 to 50 years of their lives.


We used publicly available archives of speeches given to large audiences on a semi-regular basis (generally with a couple of years between each instance). The group of speeches was given during the last 30-50 years of each speaker’s life, meaning that we have samples ranging from the speakers’ late 40s to early 90s. We extracted 5-minute samples (recordings and transcripts) from each speech. We then used the Penn forced-alignment system (this system finds and marks the boundaries of individual speech sounds) to identify word and sound boundaries. Acoustic characteristics of the speech were extracted from the speech signal using a custom script using the Praat software package.


In the present analysis, we investigate changes in the vowel space (the acoustic range of vowels a speaker has produced), fundamental frequency (what a listener hears as pitch), the duration of words and sounds (segments), and speech rate. We model the acoustic characteristics of our speakers using Generalized Additive Models (Hastie & Tibshirani, 1990), which allows for an investigation of non-linear changes over time.


The results are discussed in terms of vocal changes over the lifespan in the speakers’ later-years. Figure 1 illustrates the change in one speaker’s vowel space as he ages. We find that for this speaker the vowel space shifts to lower frequencies as he ages.


Figure 1 – An animation of Speaker 1’s vowel space and how it changes over a period of 50 years. Each colored circle represents a different decade.


We also find a similar effect for fundamental frequency across all three speakers, Figure 2, where the average fundamental frequency of their voices gets lower and lower as they age and then starts to get higher after the age of 70. This effect is the same for word and segment duration. We find that on average as our three speakers age their speech (at least when giving public speeches) gets faster and then slows down after around the age of 70.

Figure 2: Average fundamental frequency of our speakers’ speech as they age.

Figure 3: Average speech rate in syllables per second of our speakers’ speech as they age.


While on average our three speakers show a change in the progression of their speech at the age of 70, each speaker has their own unique speech trajectory. From a physiological standpoint, our data suggest that with age come not only laryngeal changes (changes to the voice) but also a decrease in respiratory health – especially expiratory volume – as has been reflected in previous studies.


2pUWb2 – Study of low frequency flight recorder detection. – I Yun Su

“Study of low frequency flight recorder detection.”


I Yun Su – r07525010@ntu.edu.tw

Wen-Yang Liu – r06525035@ntu.edu.tw

Chi-Fang Chen – chifang@ntu.edu.tw


Engineering Science and Ocean Engineering,

National Taiwan University,

No. 1 Roosevelt Road Sec.#4

Taipei City, Taiwan


Li-Chang Chuang – eric@ttsb.gov.tw

Kai-Hong Fang – khfang@ttsb.gov.tw


Taiwan Transportation Safety Board

11th Floor, 200, Section 3,

Beixin Road, Xindian District,

New Taipei City, Taiwan


Popular version of paper 2pUWb2

Presented Tuesday afternoon, December 8, 2020

179th ASA Meeting, Acoustics Virtually Everywhere


A flight recorder is installed in every aircraft to record the flight status. When the aviation accident occurs, this recorder can help clarify the cause of the incident. Furthermore, if the plane crashes into the ocean, the underwater locater beacon (ULB) inside the flight recorder will be triggered which would make a sound that could be located by the rescue team.


In 2009, there was a serious accident involving the Air French flight 447. According to the final report, French Civil Aviation Safety Investigation Authority suggested that the ULB should acquire extended transmission time up to 90 days and increased transmission range. In Taiwan, the flight recorder has already been installed with a 37.5 kHz ULB inside the tail section of every vehicle, and now Taiwan Transportation Safety Board considered to put in an additional 8.8 kHz ULB in the flight belly. (Picture 1)

Picture 1: The positions of the 37.5 kHz and 8.8 kHz ULB on the plane.


The main propose of this study is to understand the performance of the newly bought 8.8 kHz ULB – DUKANE SEACOM DK180. Firsts off, I did the simulation on both ULB to compare the detection ranges (DR), and according to the beacon specifications, the source level (SL) of the both is 160 dB re 1μPa.


For the DR to be simulated, the transmission loss (TL) which is affected by a lot of different environmental parameters must be determined first. This study is based on the Taiwan database, and using the Gaussian beam propagation to calculate the TL. After the TL is acquired, the noise level (NL) which also has certain impact on the DR has to be determined. Generally, the lower the frequency, the longer the DR. DR can be determined by passive sonar equation, and can be derive the FOM = SL – NL – DT. The DT is Detection Threshold and the FOM is Figure of Merit, which is the maximum TL that can detect. The intersection of the TL and FOM is DR. In the study, the DT is set to be zero. At the Point A, the NL of the 8.8 kHz is 78 dB re 1μPa and for 37.5 kHz is 65 dB re 1μPa, so the FOM of the 8.8 kHz is 82 dB re 1μPa and for 37.5 kHz is 95 dB re 1μPa. The DR in 8.8 kHz ULB is about twice than 37.5 kHz ULB at Point A. (Picture 2)


Picture 2: Detection Ranges of 8.8 kHz ULB and 37.5 kHz ULB in the Point A.


In the study, I have also done the experiment in Taiwan Miaoli offshore. The results also show that the newly bought 8.8 kHz ULB would have a smaller TL and longer DR. In summary, with an additional 8.8 ULB, the more precise prediction of the beacon location could be obtained.

2pBAc – Targeting Sound with Ultrasound in the Brain – Scott Schoen Jr

“Targeting Sound with Ultrasound in the Brain”

Scott Schoen Jr – scottschoenjr@gatech.edu

Costas Arvanitis – costas.arvanitis@gatech.edu

Georgia Tech

901 Atlantic Dr

Atlanta, GA 30318


Popular version of paper 2pBAc (“Spatial Characterization of High Intensity Focused Ultrasound Fields in the Brain”)

Presented Tuesday afternoon, December 8, 2020

179th ASA Meeting, Acoustics Virtually Everywhere


The pitch and size of a sound are quite intrinsically connected. This is why, for instance, low-register instruments (such as a tuba or double bass) are large, while higher pitched ones may be very small (like a piccolo or triangle). Sound travels in waves, and the product of the length of the wave (wavelength) and its pitch (frequency) is a constant (namely, the speed of sound).

Consequently, the wavelength of sounds we can hear may be between about 15 m and 0.2 cm. But just as there are wavelengths of light we cannot see (such as ultraviolet and X-rays), there exists sound with much smaller wavelengths. Ultrasound, so called since its frequency is above our hearing range, is able to travel through human tissue and enables noninvasive imaging with millimeter resolution.

Since sound is pressure, it also carries energy. And, much like sunlight through a magnifying glass, sound energy may be focused to a small area to cause heating. This technique has allowed noninvasive and minimally invasive therapy, where focused ultrasound (FUS) creates small regions of high heat or forces to burn or manipulate the tissue. This is especially important for brain diseases, where surgery is particularly challenging.

Fig. 1 – Human cells are sensitive to sound frequencies from about 20 Hz to 20 kHz (left). However, focusing sound to a small area requires small wavelengths—and thus much higher frequencies (right). Not to Scale

Interestingly, it turns out that at very high pressures, so-called nonlinear acoustic effects become important, and the sound begins to interact with itself. One consequence is that if the FUS has to very high frequencies, say 995 kHz and 1005 kHz, the focal spot will a few millimeters, similar to 1 mm. However, the high pressure interaction will also generate energy at 1005 kHz – 995 kHz = 10 kHz—within the audible and tactile range.

This work describes our use of simulations and experiments to understand how this low frequency energy might be realized for FUS through the skull. Understanding the strength and distribution of low frequency energy generated with high frequency FUS may open a new range of therapeutic and diagnostic capabilities in one of the most complex and medically imperative organs: the brain.


4aMUa3 – Musical Notes translate to Emotions? A neuro-acoustical endeavor with Indian Classical music – Shankha Sanyal

Musical Notes translate to Emotions? A neuro-acoustical endeavor with Indian Classical music

Shankha Sanyal

Samir Karmakar

Dipak Ghosh

Jadavpur University

Kolkata: 700032, INDIA


Archi Banerjee

Rekhi Centre of Excellence for the Science of Happiness

IIT Kharagpur, 721301, INDIA


Popular version of paper 4aMUa3

Presented Thursday morning, December 10, 2020

179th ASA Meeting, Acoustics Virtually Everywhere



The Indian classical music (ICM) system is based on the note system which consists of 12 notes, each having a definite frequency. The main feature of this music form is the existence of ‘Ragas’, which are unique, having a definite combination of these 12 notes, though the presence of 12 notes is not essential in each of the Raga; some can have only 5 notes which are usually called ‘pentatonic Ragas or scales’. Each Raga evokes not a particular emotion (rasa) but a superposition of different emotional states such as joy, sadness, anger, disgust, fear etc. A mere change in the single frequency of a Raga clip changes it to another Raga and also the associated emotional states change along with it. In this work, for the first time, we envisage to study how the emotion perception in listeners’ change when there is an alteration of a single note in a pentatonic Raga and also when a particular note(s) is replaced by its flat/sharp counterpart. Robust nonlinear signal processing methods have been utilized to quantify the acoustical signal as well as the brain arousal response corresponding to the two pair of Ragas taken for our study.

The two pair of ragas chosen for our study:

Raga Durga- sa re ma pa dha sa 

Raga Gunkali– sa RE ma pa DHA sa 

The notes ‘re’ and ‘dha’ of Durga is changed to their respective sharp/flat counterparts which change Raga Durga to Raga Gunkali.

Raga Durga- sa re ma pa dha sa

Raga Bhupali-  sa re ga pa dha sa 

The note ‘ma’ in Raga Durga, when changed to ‘ga’, makes the Raga Bhupali


Human Response Analysis-

A human response study was done with 50 subjects who were provided with an emotion chart of the basic 4 emotions, and were asked to mark the clips with their perceived emotional arousal.

The radar plots for the human response analysis: (Insert Radar1.jpg and Radar2.jpg here)


(Fig. 1 a-b) Pair 1

(Fig. 1 c-d) Pair 2


It is seen that the change of a single note manifests in a complete change in emotional appraisal at the perceptual level of the listeners. In the next section, EEG response of 10 participants (who were made to listen to these raga clips) has been studied using nonlinear multifractal tools. Multifractality is an indirect measure of the inherent signal complexity present in the highly non-stationary EEG fluctuations.

The following figures give the averaged multifractality corresponding to the frontal and temporal lobes in alpha and theta EEG frequency range for the two pair of raga clips. P1…P5 represents the different phrases (note sequences) in which the main changes between the two ragas have been done.



(Fig. 2 a-b) Pair 1


(Fig. 2 c-d) Pair 2


For the first pair, alpha and theta power decreases considerably in the frontal lobe, while in temporal lobes, phrase specific arousal is seen. For the second pair, the arousal is very much specific to the phrases. This can be attributed to the fact that the human response data showed the emotional arousal in second pair is not strongly opposite to each other, but a mixed response is obtained. For the first time, a scientific analysis on how the acoustic, perceptual and neural features change when the emotional appraisal is changed due to the change of a single frequency in a particular Raga is reported in the context of Indian Classical Music