Pawel Bielski – pawbiels@pg.edu.pl
Hanna Pruszko – hanprus1@pg.edu.pl
Tomasz Mikulski – tomi@pg.edu.pl
Gdansk University of Technology
Narutowicza 11/12, 80-233 Gdansk
Poland

Popular version of paper 1aMU4 Numerical and experimental assessment of string gauge influence on guitar tone
Presented Tuesday morning, June 08, 2021
180th ASA Meeting, Acoustics in Focus

Meet Adam. Adam loves the nines (that is, 0.09-inch gauge, or 9’s, named by the diameter of the high E string). When he touches a guitar stringed with the 9’s, it seems soft and responsive under his fingers. This phenomenon is called “feel”. Adam picks a guitar with a proper feel and unites with the instrument. Suddenly physical bounds disappear. Adam believes in supernatural traits of the 9’s and no research can change his mind.

But we can still try.

Guitar players are obsessed with string gauges. From the super slinky 7’s of Billy Gibbons, through the agile 8’s and 9’s of Jimi Hendrix and Jimmy Page, massive sound of Joe Bonamassa (11) and Stevie Ray Vaughan (13), to Pat Martino’s super fat 15’s and extreme twang of Dick Dale (16’s). A wide selection of string gauges covers a variety of guitar playing styles.

Thicker strings are harder to bend but carry more force. Vibration is essentially very fast bending in different modes (shapes) – 1st harmonic (fundamental) and upper harmonics (overtones). Harmonic composition is called the brightness of the string. Higher harmonics create a sharp and open sound. Lower harmonics help to beef up the tone. Definition of chords also benefits from profound fundamentals.

Fundamental mode and upper harmonics of a vibrating string [Source image: Harmonics.png]

Depending on the gauge, the total force carried by electric guitar strings ranges from the weight equivalent of a ten-year-old child to an adult man. It makes nearly triple the difference. Acoustic guitars offer a more humble selection of 10’s – 13’s string gauges, but the choice might be even more critical. The acoustic sound is raw and less processed. It depends on the physical features of the instrument. Fiddling with the pulling force and vibrating mass on a resonant guitar body must make a difference. The body gets tenser and stiffer. It is driven hard and significantly deformed. Will it be able to breathe freely?

Imagine borrowing your general practitioner’s stethoscope and listening to the acoustic guitar’s soundboard while it plays. This is roughly how we used accelerometers. Low E strings of different gauges were repeatedly tested for their volume, sustain (duration of sound), and harmonic composition. The samples were recorded with a microphone too. We analyzed the sound spectrum during different stages of the sound.

Setup of accelerometers [Source image: AccSetup.png]

Most findings agree with the general beliefs regarding string gauges besides one major exception. The weak sustain of heavy strings might be a surprise to many guitar players. Thick strings have a rich and loud attack yet immediately lose their superb qualities. They seem to excel at quick, punchy notes, but struggle with slow-paced singing solos. In the long run, light strings were more sustainable, retaining their harmonics in time.

[Recording of 13’s string: E6nr13.mp3]

[Recording of 10’s string: E6nr10.mp3]

Recordings of heavy and light strings (flanger effect caused by averaging from multiple samples

Advantages of the different gauges shown at two scales [Source image: Signals.png]

Other than that, heavy strings are generally louder and more substantial, while light strings seem brighter and more open. Thick strings excite the body modes (structural vibration) more, while light ones favor air resonance.

Adam will probably not readjust his beliefs, but maybe you will?

Summary of the findings

Jim Woodhouse — jw12@cam.ac.uk
Cambridge University Engineering Department
Trumpington St
Cambridge CB2 1PZ, U.K.

Nicolas Lynch-Aird — lynchaird@yahoo.co.uk
The Old Forge
Burnt House Lane
Battisford
Suffolk IP14 2ND, U.K.

Popular version of paper ‘2pMU3’ String choice: Why do harpists still prefer gut?
Presented Wednesday afternoon, June 9, 2021
180^th ASA Meeting, Acoustics in Focus

Classical guitarists have all abandoned traditional gut strings in favour of nylon, but harpists still prefer gut.  Why is this? A study of the various limits on string choice for musical instruments has shown that the answer lies in a difference of “damping” in the strings, which is responsible for a difference in brightness of the sound.

When choosing a string for an instrument, the player knows the string length and the frequency it will be tuned to: their task is to choose the material and the diameter. The various different constraints on that choice can be summarised in a chart: a schematic version is shown here.

Schematic chart for choosing strings for musical instruments

The length and the frequency multiplied together defines the position on the horizontal axis. The player’s choice then consists of moving along a vertical line through that point, to choose a string diameter. They need to make a choice within the blue region, otherwise something will go wrong.  The exact shape and position of this blue region depends on the choice of string material.

Obviously the string must not break. There are also upper and lower limits on the tension: if a string is too slack or too tight, it feels wrong to the player.  Less obviously, the choice must lie beneath the dashed line labelled “damping too high”, otherwise the sound will become a dull thud rather than a ringing musical tone. This is where the harp differs from the guitar.  Guitar strings stay well clear of the dashed line, but for the longer, lower-pitched strings of a harp, players want to use strings with very high tension so that the “feel” is right. But that pushes them towards the dashed line, and it is this damping limit that defines the practical limit on string choice. When the detailed charts are compared for nylon and  gut strings, the dashed line is higher for gut. That gives a bit more “headroom” for the player’s choice, and allows them to choose a string that feels good under the fingers, while still having a satisfyingly bright and ringing tone.

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 Emotions from musical notes? A psycho-acoustic exploration with Indian classical music
Presented Thursday morning, December 10, 2020
179^th ASA Meeting, Acoustics Virtually Everywhere
Read the article in Proceedings of Meetings on Acoustics

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:

(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

Archi Banerjee – archibanerjee7@iitkgp.ac.in
Priyadarshi Patnaik – bapi@hss.iitkgp.ac.in
Rekhi Centre of Excellence for the Science of Happiness
Indian Institute of Technology Kharagpur, 721301, INDIA

Shankha Sanyal – ssanyal.ling@jadavpuruniversity.in
Souparno Roy – thesouparnoroy@gmail.com
Sir C. V. Raman Centre for Physics and Music
Jadavpur University, Kolkata: 700032, INDIA

Popular version of paper 4aMUa1 Lyrics on the melody or melody of the lyrics?
Presented Thursday morning, December 10, 2020
179^th ASA Meeting, Acoustics Virtually Everywhere
Read the article in Proceedings of Meetings on Acoustics

The musicians often say “When a marriage happens between a lyric and a melody, only then a true song is born”! But, which impacts the audience more in a song – Melody or lyrics? The answer to this question is still unknown. What happens when the melody is hummed independently without the lyrics? How does that affect the acoustical waveform of the original song? Does the emotional appraisal remain same in both cases? The present work attempts to answer these questions using songs from different genres of Indian music. Recordings of two pairs of contrast emotion (happy-sad) evoking Raga bandishes from Indian Classical Music (ICM) and one pair of Bengali contemporary songs of opposite emotions (happy-sad) were taken from an experienced female professional singer who was asked to consecutively sing (with proper meaningful lyrics) and hum (without using any lyric or meaningful words) the songs, keeping the melodic structure, pitch and tempo same. In ICM, the basic building blocks are Ragas – bandish is a song composed in a particular Raga. The chosen audio clips are:

Audio 1(a,b): Sample audios of (a) Humming and (b) Song versions of same melodic part

a)

b)

Figure 1(a,b): Sample acoustical waveforms and pitch contours of (a) Humming and (b) Song versions of same melodic part

Next, using different sets of humming-song pairs from the chosen songs as stimuli, Electroencephalogram (EEG) recordings were taken from 5 musically untrained participants who understand the languages Hindi (of bandishes) and Bengali. Both music and EEG signals have highly complex structures, but their inherent geometry features self similarity or structural repetitions. Chaos based nonlinear fractal technique (Detrended fluctuation analysis or DFA) was applied both on the acoustical waveforms and their corresponding EEG signals. The changes in self similarity were calculated for each humming-song pair to study the impact of lyrics both in acoustical and neurological levels.

a)

b)

Figure 2(a,b): Variation in DFA scaling exponent in acoustical signals of humming-song pairs taken from songs of (a) Indian Classical music and (b) Bengali contemporary music

Acoustical analysis revealed that in songs where the lyrics is highly projected or emphasized (slow tempo vilambit bandish and Bengali contemporary songs), the DFA scaling exponent or self similarity decreases from humming to song version if the melodic pattern remains same. The sudden and spontaneous fluctuations in the pitch and intensity levels of the song versions due to the introduction of several consonants, rhythmic variations and pauses between words embedded in the lyrics may help in lowering the scale of self similarity.

a)

b)

Figure 3(a,b): Average of differences in DFA scaling exponent in (a) Frontal electrodes (F3, F4, F7, F8 & FZ) and (b) Occipital (O1 & O2), Parietal (P3 & P4) and Temporal (T3 &T4) electrodes for different Humming-Song pairs of Bengali contemporary songs

EEG analysis revealed that for both genres of music, in songs with highly projected lyrics, self similarity in frontal lobe electrodes increases from humming to song version of the same melody; whereas in occipital, temporal and parietal electrodes, we observed an increment in DFA scaling exponent from humming to song for the slow tempo songs and a decrement in the same for high tempo songs.

Combining results of acoustic analysis and EEG analysis, the impact of lyrics was found to be significantly higher in lower tempo songs compared to higher tempo songs both in acoustical and neuro-cognitive level. This is a pilot study in the context of Indian music which endeavors to quantitatively analyze the contribution of lyrics in songs of different genre as well as different emotional content in both acoustical and neuro-cognitive domain with the help of a unique scaling exponent.