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Modern Recording Techniques > Chp. 2 Sound and Hearing > Flashcards

Chp. 2 Sound and Hearing Flashcards

1
Q

What is a sound pressure level (SPL)?

A

Sound pressure level is the acoustic pressure that is built up within a defined atmospheric area. The higher the SPL, the louder the sound.

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2
Q

In terms of the production of sound energy, what is compression?

A

Compression occurs when a vibrating mass moves outward from its normal resting state and squeezes the air molecules closer together in an area away from the sound source. The area being squeezed together has a greater than normal atmospheric pressure.

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3
Q

What is rarefaction?

A

Rarefaction is created as an opposite reaction to compression. It is the formation of an area of lower-than-normal atmospheric pressure.

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4
Q

What is a sound wave or wave propagation?

A

A sound wave or wave propagation is the movement of sound energy through the atmosphere that continues to push outward against areas of lower pressure.

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5
Q

What is a wave form?

A

A wave form is the graphic representation of a sound-pressure level (SPL) or voltage level as it moves through a medium over time.

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6
Q

What are the fundamental characteristics of a waveform?

A

The fundamental characteristics of a waveform are: Amplitude, Frequency, Velocity, Wavelength, Phase, Harmonic content and Envelope.

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7
Q

What is amplitude level?

A

Amplitude level is the distance above or below the centerline of a waveform. The greater the distance or displacement from the centerline, the more intense the pressure variation, electrical signal level or physical displacement will be within a medium.

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8
Q

What is a peak amplitude value or peak level?

A

Peak amplitude value is the measurement of either the maximum positive or negative signal level of a wave.

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9
Q

What is the peak-to-peak value of a wave?

A

The peak-to-peak value of a wave is the total measurement of the positive and negative peak signal levels.

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10
Q

What is the root-mean square (rms) value?

A

The root-mean square (rms) is used to determine a meaningful average level of a waveform over time–one that more closely approximates the level that is actually perceived by our ears and gives a better real-world measurement of overall signal amplitudes. The rms is calculated by squaring the amplitudes at points along the waveform and then taking the mathematical average of the combined results. The rms value is always positive.

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11
Q

What is a cycle?

A

A cycle is one completed excursion of a wave.

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12
Q

What is a Hertz (Hz)?

A

A Hertz is the number of cycles that occur within a second.

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13
Q

What is a frequency?

A

Frequency is the rate at which an acoustic generator, electrical signal or vibrating mass repeats within a cycle of positive and negative amplitude.

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14
Q

What is velocity?

A

Velocity is the speed of something measured in feet/second. The velocity of a sound wave as it travels through air at 68 degrees F (20 degrees C) is approximately 1130 ft/sec or 344 meters/second. This speed is temperature dependent, and increases at a rate of 1.1 ft/sec for each Fahrenheit degree increase in temperature (2 ft/sec per Celcius degree).

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15
Q

What is a wavelength of a waveform?

A

The wavelength of a waveform is the physical distance in a medium between the beginning and the end of a cycle.

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16
Q

What is the period of a wave?

A

The period of a wave is the time it takes to complete one cycle.

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17
Q

What is the formula for determining the length of a waveform?

A

T=1/f
where T is the number of seconds per cycle, and f is the frequency in hertz.
Ex. 1. Calculate the length of a 30Hz waveform: 1130/30=37.6 ft.
Ex. 2. Calculate the length of a 300Hz waveform: 1130/300=3.76 ft.

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18
Q

What is one of the cornerstones of the study of acoustics?

A

One of the cornerstones of the study of acoustics is that sound reflects off a surface boundary at an angle that is equal to and in an opposite direction of its initial angle of incidence.

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19
Q

What is a frequency response curve?

A

A frequency response curve is the charted output of an audio device. The curve is used to graphically represent how a device will respond to the audio spectrum, and thus how it will affect a signal’s overall sound.

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20
Q

What is phase shift?

A

Phase shift is a term that describes one waveform’s lead or lag time with respect to another.

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21
Q

What is a partial?

A

A partial is a frequency that exists in addition to the fundamental pitch that is being played. Partials help you to differentiate between instrumental voicings.

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22
Q

What are upper partials or overtones?

A

Upper partials or overtones are partials that are higher than the fundamental frequencies.

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23
Q

What are harmonics?

A

Harmonics are partials that are whole-number multiples of the fundamental frequency.

Ex. In the case of a 440 Hz fundamental frequency, it is technically the first harmonic because it is 1 times the fundamental frequency. The 880 Hz wave is called the second harmonic, etc.

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24
Q

What is an even harmonic?

A

An even harmonic is a frequency that is an even multiple of the fundamental frequency. Even harmonics create a pleasing sound to the ear.

Ex. 440 Hz, 880 Hz, 1760 Hz.

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25
Q

What is an odd harmonic?

A

An odd harmonic is an odd multiple of the fundamental frequency. Odd harmonics create dissonance.

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26
Q

What is a simple wave?

A

A simple wave is a kind of musical waveform that includes square waves, triangle waves and sawtooth waves. They contain a consistent harmonic structure. They are said to simple because they are continuous and repetitive in nature.

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27
Q

What is a complex wave?

A

A complex wave is often not symmetrical about the zero line, and does not necessarily repeat. An example of a complex wave form is one that is created by any naturally occurring sound such as music or speech.

28
Q

What is timbre?

A

Timbre are the harmonics and their relative intensities which determine an instrument’s character.

29
Q

What is an amplitude envelope?

A

The amplitude envelope can be described as the characteristic variations in level that occur in time over the duration of a played note. Amplitude envelope is a characteristic of a musical instrument that works in combination with timbre to determine its unique and subjective sound.

30
Q

What are the four sections of an envelope of an acoustically or electronically generated signal?

A

Attack, decay, sustain and release.

31
Q

In terms of the amplitude envelope, what is an attack?

A

An attack refers to the time taken for sound to build up to its full volume when a note is initially sounded.

32
Q

In terms of an amplitude envelope, what is decay?

A

Decay refers to how quickly the sound levels off to a sustain levelafter the initial attack peak.

33
Q

In terms of an amplitude envelope, what is sustain?

A

Sustain refers to the duration of the ongoing sound that is generated following the initial attack decay.

34
Q

In terms of an amplitude envelope, what is release?

A

Release relates to how quickly the sound will decay once the note is released.

35
Q

What is a decibel?

A

A decibel is the unit of measure used to determine the sound pressure level (SPL), signal level and relative changes in signal level. It literally means 1/10th of a Bell (an old telephone transmission loss measurement unit). For practical purposes, it is the logarithmic value that expresses differences in intensities between two levels.

36
Q

What is a logarithm?

A

A logarithm is a mathematical function that reduces large calues into smaller more manageable numbers.

37
Q

What is the log of 2?

A

The log of 2 is 0.3

38
Q

What is the log of 1/2?

A

The log of 1/2 is -0.3

39
Q

What is the log of 0.1?

A

The log of 0.1 is -1

40
Q

What is the log of 0.01?

A

The log of 0.01 is -2

41
Q

What is the log of 0.001?

A

The log of 0.001 is -3

42
Q 
What are the logs for the numbers listed below?
10,000,000,000,000
1000
100
10
A

13
3
2
1

43
Q

What is the threshold of hearing?

A

The threshold of hearing is the softest sound the average person can hear. Most conversations will have ans SPL of 70 dB. The average home stereo is played at between 80 and 90 dB SPL. Sounds that are painful range between 130 and 140 dB SPL or more. The threshold of hearing is equal to 0.0002 microbars. This threshold level is denoted as 0 dB SPL.

44
Q

What is voltage?

A

Voltage is thought of as the pressure behind electrons within a wire.

45
Q

What is power?

A

Power is usually a measure of wattage or current, and can be thought of as the flow of electrons through a wire over time.

46
Q

What is a transducer?

A

A transducer is any device that changes one form of energy into another, corresponding form of energy.

47
Q

What part of the ear collects sound pressure waves and funnels them into the aural canal?

A

The pinna is the part of the ear that collects sound pressure waves and funnels them into the aural canal.

48
Q

What is the purpose of the eardrum?

A

The eardrum sits at the bottom of the aural canal and receives sound pressure waves funneled in to it by the pinna of the outer ear. The eardrum is a membrane that changes sound waves into mechanical vibrations.

49
Q

What is the purpose of the three bones in the middle ear that are referred to as the hammer, the anvil and the stirrup?

A

The purpose of the hammer, the anvil and the stirrup is to amplify the mechanical vibrations of the eardrum and transfer that energy to the cochlea located in the inner ear. The hammer, anvil and stirrup also act as a limiter in that that reduce the level of loud, transient sounds.

50
Q

What is the purpose of the cochlea?

A

The cochlea contains two fluid-filled chambers that receive the energy from the hammer, anvil and stirrup. These chambers also contain cilia.

51
Q

What are cilia, and what is their purpose?

A

Cilia are the hair-like nerve cells that sit inside the chambers of the cochlea. They respond to sound frequencies based on their placement along the cochlea. Cilia are the nerve endings that send the neural stimulations to the brain which then interprets the sensations as hearing.

52
Q

What is the threshold of feeling?

A

The threshold of feeling is the SPL that causes discomfort in a listener 50% of the time. This is approximately 118 dB SPL between the frequencies of 200 Hz and 10 KHz.

53
Q

What is acoustic trauma?

A

Acoustic trauma is a condition that occurs when the ear is exposed to a sudden, loud noise in excess of 140 dB. This can lead to permanent hearing loss.

54
Q

What is a temporary threshold shift?

A

A temporary threshold shift is a condition where the ear experiences temporary hearing loss when exposed to long-term, loud noise.

55
Q

What is permanent threshold shift?

A

Permanent threshold shift is a condition where extended exposure to loud noises in a specific hearing range can lead to permanent hearing loss in that range.

56
Q

What is psychoacoustics?

A

Psychoacoustics is the area of study dealing with how and why the brain interprets a particular sound stimulus a certain way.

57
Q

What are beats?

A

When two tones that differ slightly frequency are played at the same time they exhibit a phenomena know as beats. In reality, beats are a result of the ear’s inability to separate closely pitched notes. This results in a third frequency created from the phase sum and difference values between the two notes.

58
Q

What is a combination tone?

A

A combination tone results when two loud tones differ by more than 50 Hz. In this case the ear perceives an additional set of tones that are equal to both the sum and the difference between the two original tones.

59
Q

What is masking?

A

Masking is the phenomenon by which loud signals prevent the ear from hearing softer sounds.

60
Q

What is spacial or binaural localization?

A

Spacial or binaural localization is the capability of two ears to localize a sound source within an acoustic space.

61
Q

What is an inter aural arrival time difference?

A

An interaural arrival time difference is the method the method of localization our brain must rely on to determine location of loer frequency sounds.

62
Q

What is panning?

A

Panning is the illusion of physical positioning between speakers.

63
Q

What is direct sound?

A

Direct sound is a wave that travels the shortest distance from the source to the listener.

64
Q

What is early reflection?

A

Early reflection is a wave that bounces off of surfaces within the room before reaching the listener.

65
Q

What is reverberation?

A

Reverberation occurs whenever room reflections continue to bounce off of room boundaries and a randomly decaying set of sounds can be heard after the source stops.

Modern Recording Techniques (2 decks)

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