Basic Acoustics Study Guide

Question 1

Acoustic flow

Answer 1

Acoustic flow refers to pressure sound wave propagation, which travels at the speed of sound. Acoustic flow is what carries the sound signal to listeners.

Question 2

Formant

Answer 2

Frequency peaks in the radiated spectrum

Question 3

Formant-harmonic tuning

Answer 3

Formant-harmonic tuning refers to reshaping the vocal tract by means of articulation to adjust its resonances to obtain better matches between tube resonances and available source harmonics

Question 4

Harmonics

Answer 4

Individual frequency components of a periodic waveform (or “clean” phonation): also referring to the harmonic series; all integral multiples of the fundamental frequency.

Question 5

Inertance

Answer 5

When the energy is kinetic (due to motion), as in the inertial energy stored in the velocity of the air flow at a constriction in the vocal tract, the reactance (resistance to the flow motion) is referred to as an inertance

Question 6

Loudness

Answer 6

Human perception of intensity, which varies by frequency since human hearing sensitivity varies by frequency, peaking between 2000 & 4000Hz. It is adjusted by the threshold of human hearing (10 decibels higher than sound level measures)

Question 7

Maximum Flow Declination Rate (MFDR)

Answer 7

How rapidly airflow rate changes from peak flow to zero flow

Question 8

Resonance

Answer 8

In reference to voice, the amplification and modification of the voice source waveform by the vocal tract (throat, mouth, and nasal cavity).

Question 9

Singer’s formant

Answer 9

The singer’s formant is a resonance created by clustering the third, fourth and fifth vocal tract formants together within a narrow frequency range approximately around 2,300-3,500Hz. The clustering of the formants provides amplification of the harmonics within this range.

Physiologically, it is believed that this is a result of narrowing the epilaryngeal tube exit relative to pharyngeal openness. This allows the voice to project through the masking effect of the orchestra on spectral content below ca. 500Hz.

Question 10

Sound intensity

Answer 10

Raw power (watts per square meter)

Question 11

Sound level

Answer 11

The (logarithmic) decibel measure of the intensity relative to a given 0 decibel marker

Question 12

Spectral slope

Answer 12

The rate at which harmonics above the fundamental frequency weaken in intensity, stated in negative dBs/octave. Also called spectral tilt or roll-off.

Question 13

Vocal tract resonances

Answer 13

Peak frequency responses of the vocal tract to sound input

Question 14

Vibrato

Answer 14

The two main acoustic metrics of vibrato are rate and excursion or extent (with amplitude as a less prominent third). Rate refers to the number of frequency oscillations per second, and excursion, to how far above and below the center (target) frequency the tone travels during an oscillation. If these parameters are within certain limits, listener perception of pitch can remain steady—referred to as vibrant “singleness of pitch.” If the rate slows below ca. 5/sec and the excursion widens beyond plus or minus a semitone, percept of pitch steadiness is compromised.

Question 15

Vowel modification

Answer 15

As pitch ascends, its harmonic set rises, causing its changing frequencies to migrate through their inherent spectral tone color gradients; furthermore, as source harmonics move into and through vocal tract resonance peaks, their intensity rises and falls, changing their individual contribution to the overall, composite tone color and vowel percept. This is especially evident when harmonics rise into and through the first resonance (F₁)