Acoustics & Instrumentations Comp Study

____ is the amount of matter present

Mass

____ is the amount of mass per unit volume

Density

____ is a property that enables recovery from distortion of shape or volume

Elasticity

____ is the amount of force per unit area

Pressure

Atmospheric pressure is ____ at seal level than it is at 30k feet above sea level

GreaterI

In order to vibrate, both the source and transmitting medium share these physical properties

Mass and elasticity

Sound is considered a _____ wave

longitudinal

The swaying back and forth motion of molecules (oscillations) describes

Simple harmonic motion

Waveform amplitude can be measured the following ways

Peak amplitude, peak to peak pressure, RMS (root mean square) amplitude

The difference between what is considered a simple sound vs complex sound is

How many frequencies are present

Telephone audio is considered to be this kind of frequency filter

Band-pass

The time it takes to complete a single waveform cycle is called

Period

____ represents the point in the cycle at which the vibrating object is located at a given instant in time

Phase

Low frequency waveforms have ___ wavelengths, whereas high frequency waveforms have ___ wavelengths

Longer, shorter

An ____ is a very quiet room achieved by reducing reflected sound from the floor and the ceiling

Anechoic chamber

A longitudinal wave produces particle displacement in a medium that is ___ to the direction of wave propogation

Parallel

Something that can produce a change in matter is ____

Energy

____ is the reactionary force to ___

Elasticity, inertia

____ is a random molecular motion as molecules maintain distance from each other

Brownian motion

What is it called when peaks of the wave form are cut off due to amplifier circuits being over driven>

Peak clipping

Imagine a clinician administering the Quick Speech in Noise Test (QuickSIN) to a patient. They are presenting the sentences at 70dB SPL and the competing noise is presented at 60dB SPL. What is the signal to noise ratio (SNR?

10dB

A tuning fork is an example of a ____ sound, consisting of a single frequency, where as speech is an example of a ____ sound, consisting of multiple frequencies

Simple; Complex

Acoustical energy turns into thermal energy when it encounters fricitional resistance (frictional force) in the air (T/F)

True

___ refers to diminishing amplitude of a vibration over time due to a frictional forces

Damping

The distance that a sound wave travels during one complete cycle of vibration is called

Wavelength

The speed of sound is faster than the speed of light (T/F)

False

The speed of sound ____ as air temperature decreases

Decreases

Spherical wave front amplitude ____ as the wave front travels further from the sound source

Decreases

A spherical wave front eventually becomes a plane wave front once the wave front is a considerable distance from the sound source T/F

True

What is root mean square (RMS) amplitude used for

Calculating the average intensity of a sound over a period of time

The ____ explains how sound decreases in intensity as it travels further from the source

Inverse Square Law

Buildings are sometimes designed with ___ surfaces to concentrate reflected sound energy at a focal point

Concave

_____ describes why the pitch of an ambulance siren increases as it approaches the listener and decreases as it moves away from the listener

Doppler effect

The unit typically used to measure frequency is ___

Hertz

The perceptual correlate of a sound’s frequency is ___

Pitch

The perceptual correlate of a sound’s amplitude is ___

Loudness

If the time it takes to complete 2 periods is 2msec, what is the frequency of this sine wave?

F=1/T, T=seconds, F=1 period, 0.01msec → sec, F=1/.001= 1000 Hz

What are the necessary components for sound to exist?

Sound source, energy, a transmitting medium that’s elastic

Describe the relationship between uniform circular motion and a sine wave

Uniform circular motion has a direct relation to sine wave as each point on the wave correlates to the points on the circle, moving counter clockwave

How many micropascals are in 1dB?

20 micropascals

How does stiffness and density of a medium impact the speed of sound?

The stiffer the medium, the faster the speed. The less dense, the faster the speed. Stiffness is related to elasticity, and an object can be more dense but due to the stiffness it’s more elastic.

What’s the spring mass model?

This model shows that if a spring (the medium) between two masses are stiffer, the sound/energy is able to travel between each mass faster.

What are the axes of a waveform?

Amplitude over time

What are the axes of a spectrum?

Amplitude over frequency

What are the axes of a spectrogram?

Frequency over time, with amplitude

Why does sound travel farther with wind than against wind?

Sound travels farther with wind since wind bends the wave downward, refracting it into the ground reflecting up off the ground. This repeats with a skipping stone property. when it moves against the wind, it refracts the wave upward, and has nothing to reflect back off of so it scatters the energy

In a source-filter model of speech production, what is considered the filter?

Vocal tract

F0 and H1 both refer to the fundamental frequency T/F

True

__ are multiples of the fundamental frequency

Harmonics

The lips, mouth, and teeth are examples of ____

Articulators

In the context of speech, the intensity of harmonics ___ as frequency ___

Decreases, increases

____ are vocal tract resonances

Formants

Children generally produce a ____ fundamental frequency compared to adults

Higher

If the fundamental frequency is 120 Hz, what is H2?

240 Hz

F0 provides us with age and sex cues of the speaker

True

A shorter vocal tract length will typically produce lower-frequency formant values (T/F_

False

The following is a definition of ___: When the frequency of the external force matches the

natural frequency of the object or system it can lead to a significant increase in the

amplitude of vibrations

Resonance

Larger cavities/spaces generally have ___ resonant frequencies, smaller cavities have a ___ resonant frequencies (based on particle velocity and wavelength)

Lower, Higher

Formant 1 is determined most by

Tongue height

Formant 2 is determined most by

Tongue forwardness

Unvoiced consonants have ___ voice onset times (VOT) than voiced consonants

Longer

____ describes the frequency distribution of energy for speech produced over a brief period of time (1-2 minutes)

Long term average speech spectrum (LTASS)

Articulatory changes during speech production influence ____ frequencies due to changes in resonant properties of the vocal tract. These changes result in the perception of different vowel sounds

Formant

Changes in the ____ affect formant 1 and changes in the ___ affect formant 2

Pharynx, oral cavity

In a standing wave, the antinode is an area of minimal particle placement, whereas a node is a region of maximal particle displacement

False

What is destructive interference?

Playing two waves/sounds inverse from each other, creating no wave

What is a constructive interference?

Playing two of the same waves/sounds and it amplifying it

In the context of pseech production, what is meant by the concept of voiced vs unvoiced?

Whether or not the vocal folds are vibrating

Consonants are typically classified by

Place, manner, voicing

The ____ states that the sampling frequency required for a given application msut be at least twice that of the highest frequency of interest in the output signal, in other words, at least two samples per cycle are required

Nyquist theorem

Sampling frequency is the number of ___ taken from a continuous signal over a period of time (typically one second)

Digital sampled values

By following the Nyquist theorem, what is the minimum sampling rate required to accurately digitize analog frequencies from 20Hz-20kHz?

40k samples/second

This occurs when a signal is sampled at a frequency that is insufficient for the application

Aliasing

What is the psychoacoustic phenomenon where sounds are generally perceived as distinct categories?

Categorical perception

What’s a high bit rate digital signal?

The signal has multiple bits (it looks like a whole lotta stairs)

What’s a low bit rate signal?

Less quality, low amount of bits, looks like steep ass stairs

A discrete signal may also be referred to as a ____?

Digital signal, looks like dashed liines

Continuous signals may also be referred to as a _____

Analog signal

The unit typically used to measure frequency is ____

Hertz

A _____ is a device integrated or used with a microphone to reduce the distortions produced from plosive sounds like /p/ and /t/

Pop filter

The ___ refers to an increase in microphone sensitivity for low-frequencies as a subject reduces the distance between themselves and the microphone

Proximity effect

A microphone that is equally sensitive to sound from all directions has a ___ polar pattern where as a microphone more sensitive to sound directly in front of it and less sensitive to sound in front of it has a ___ polar pattern

Omni, cardioid

The difference between input voltage (Vi) and output voltage (Vo) is ____

Gain

A ___ occurs in a room or cavity when reflected sound waves interfere with incident sound waves, producing nodes and antinodes. When using loudspeakers in our sound booths, we must ensure our test subjects are not seated in locations affected by these

Standing wave

A general measure of how much speech information a patient hears is referred to as the ____

Speech Intelligibility Index

An object with a high Q-factor dampens quickly, where as an object with a low Q-factor dampens slowly T/F

False

TRS (tip-ring-sleeve) cables are designed to carry stereo signals whereas TS (tip-sleeve) cables are designed to carry mono signals T/F

True

A loudspeaker with a built-in amplifier is referred to as an _______

Active loudspeaker

The very thin component of a microphone that is displaced by varying sound pressure levels is called a ____

Diaphragm

A ____ is an image depicting the sequence an elecrical signal will pass through an electrical circuit or system

Block diagram

What’s the difference between electrical voltage versus electrical current

The electrical voltage is the pressure pushing through the wire for the electrons

The electrical current is the rate of the electrons’ movement through the wire, this can change based on the gauge of the wire

What is a dynamic microphone

A dynamic microphone has the input signal vibrate the diaphragm which vibrates a coil that interacts with a magnetic field, creating an electrical voltage that mimics the acoustic wave.

What’s a condenser microphone

A condenser microphone includes a suspension system that limits the pickup of unwanted sound (movement), and as the input signal vibrates the diaphragm, it changes the capacitance in between the diaphragm and an electrically charged backplate, which produces an electrical signal that mimics an acoustic wave

What causes acoustic feedback, and what could you do to reduce susceptance to acoustic feedback?

Signal going through the mic and through the loudspeaker is re-entering the microphone and creating a loop of re-amplification because of the loudspeaker is facing too close to the mic.

To reduce susceptance, face the loudspeaker outward away from the microphone or re-position the mic to be further from the loudspeaker

What’s the source filter theory

The source has its fundamental frequency with harmonics, then is put through a filter and produces the output with formants and different energy bends.

What are formants

The formants are where the signal has the most intensity and resonance.