The exam will last 75 minutes, including the distribution of these pages, your reading these instructions, and your handing in the completed exam. Put these stapled pages, back page up, into the alphabetical trays, and put the NCS answer sheet into the single tray on the lecture table.

Grade scale: Each of the 33 multiple choice question is worth 2 points; each part of problems 34 and 35 is worth 3 points; one point for filling your name in properly and legibly; making for an exam total of 100 points.

1. A complex tone is synthesized from sine waves of frequencies corresponding to an overtone series. What is least important for the timbre (or sound quality) of the synthesized wave (as perceived by a typical listener)?

1. the amplitude of the fundamental
2. the amplitude of the higher harmonics compared to that of the fundamental
3. the the relative phases of the harmonics
4. the presence of a formant region in the spectrum
5. the presence or absence of even harmonics

1. any wave that can be analyzed into single-frequency components can also be synthesized from these components
2. any periodic wave with some frequency f can be synthesized from sine waves of the frequency f and its harmonics
3. the amplitudes and phases of a complicated wave shape are related by a simple formula
4. any wave containing harmonics of some fundamental frequency f will repeat itself with a periodicity T = 1/f
5. none of the above

1. a different amplitude of the fundamental
2. a different amplitude of the second harmonic
3. no higher (N > 1) harmonics whatever
4. a formant at harmonic N = 3
5. there is no difference between the spectra

1. discrete peaks in an overtone series with sizes decreasing by steps of 3 for each octave increase in frequency
2. discrete peaks in an overtone series with sizes decreasing by a factor of 3 for each octave increase in frequency
3. some amplitude at all frequencies, and with total power in each octave 1/3 of that in the previous octave
4. some amplitude at all frequencies, and with total power in each octave 1/2 of that in the previous octave
5. equal amplitude in every third octave

1. a Helmholz resonator
2. an open tube
3. a closed tube
4. a sounding board
5. a receptacle for more wine

1. a single, low, isolated resonant frequency
2. resonances at odd harmonics only
3. resonances even harmonics only
4. the absence of a fundamental
5. multiple closely spaced resonance frequencies

1. 100 Hz, 300 Hz, and 500 Hz
2. 100 Hz, 200 Hz, and 300 Hz
3. 100 Hz, 200 Hz and 400 Hz
4. 100 Hz, 300 Hz, 500 Hz, and all other odd numbers × 100 Hz
5. 100 Hz only

1. all equal (independent of frequency)
2. decreasing with frequency
3. increasing with frequency
4. only a single amplitude was needed
5. none of the above

1. phase errors made the wave lopsided
2. amplitude errors made the tops and bottoms rounded rather than flat
3. frequency errors gave an unsteady wave shape
4. the synthesizer could not put out all the necessary high frequencies, so the synthesized wave had small rapid wiggles at top and bottom
5. we DID get a perfect square wave

1. AM
2. PM
3. FM
4. PWM
5. S&M

1. VCA
2. VCO
3. VCF
4. VCR
5. VAT

1. only F + f_m
2. only F - f_m
3. both F + f_m and F - f_m
4. F, F + f_m and F - f_m
5. all frequencies between F + f_m and F - f_m

1. generate the audio signal
2. achieve a vibrato effect
3. as a substitute for the keyboard
4. control the attack and decay characteristics of the synthesizer output
5. generate envelopes in which to mail payments for the synthesizer

1. a low-pass filter
2. a high-pass filter
3. a bandpass filter
4. a notch filter
5. a coffee filter

1. a low-pass filter
2. a high-pass filter
3. a bandpass filter
4. a notch filter
5. an oil filter

1. because people prefer band music to single-instrument music
2. because an AM modulated signal contains a band of frequencies around the station's carrier frequency
3. because a single-frequency filter would cause unwanted phase shifts in its output
4. because only bandpass filters can be tuned to different carrier frequencies
5. because AM radios developed from crystal sets, which are resonant in a band of frequencies

1. the flute has a reasonably long attack and the guitar has a very rapid attack
2. the flute has a steady-state sustain level, whereas the guitar has only attack and decay (or release)
3. the flute's decay time is much shorter than the guitar's
4. all of the above
5. none of the above

1. noise generator and AM modulation
2. noise generator and FM modulation
3. square wave generator and AM modulation
4. square wave generator and FM modulation
5. filtered sawtooth generator and AM modulation

1. use modulation
2. have a keyboard
3. control attack and decay
4. have an analog output
5. all of the above

1. amplitude modulated
2. frequency modulated
3. both amplitude and frequency modulated
4. pulse width modulated
5. all of the above

1. 1 dB
2. 3 dB
3. 10 dB
4. 30 dB
5. 100 dB

1. ¹/₃
2. 1
3. 3 ¹/₃
4. 10
5. 33

1. the outer ear
2. the middle ear
3. the cochlea
4. the basilar membrane
5. the hair cells

1. the quality of a sound depends on the place where it is emitted
2. for each sound amplitude there is a different place in the brain where it is received
3. we place the source of a sound by observing the phase difference between the waves to our two ears
4. only one place in each wave shape triggers nerve signals
5. the frequency of a sound is correlated with a place where it is most strongly received

1. They are about equal
2. The critical band is much smaller than the JND
3. The JND is much smaller than the critical band
4. The two refer to different frequency variables and cannot be compared
5. The JND has been long been criticised, but the critical band has only just been noticed

1. at all audible frequencies
2. at frequencies below about 100 Hz
3. in the middle frequency range, 100-1000 Hz
4. in the range of greatest sensitivity, 1000-5000 Hz
5. above 5000 Hz.

1. 52 dB
2. 53 dB
3. 56 dB
4. 100 dB
5. depends on the tones' frequencies

1. 52 dB
2. 53 dB
3. 56 dB
4. 100 dB
5. 200 db

1. It states that the acoustical tension equals the product of acoustical resistance and acoustical current
2. it states that the sound quality of a complex tone depends on the amplitude and relative phases of its harmonics
3. it has limitations, as demonstrated by second-order or quality beats
4. it states that each tone quality corresponds to a unique wave shape
5. all of the above

1. masking
2. ordinary (first-order) beats
3. critical bands
4. periodicity pitch
5. sharpening

1. the flow velocity is greatest where the cross sectional area is least
2. the pressure increases when the fluid's cross sectional area is decreased
3. the pressure is lower where the flow velocity is greater
4. the pressure increases as the flow velocity increases
5. the pressure increases as the depth of fluid increases

1. a formant region
2. a region of emphasis
3. a resonant region
4. a region of inharmonicities
5. a vowel sound

1. the vocal folds vibrate more rapidly in helium
2. Bernoulli's principle is valid only in air, not in helium
3. not having air to breathe leads to an anxious, higher-than-normal speech
4. the sound waves from the person travel faster in helium than in air, hence arrive more quickly at the listener
5. the frequency of the vocal formants is increased because f = S/l, S increases, and l remains the same.

I pledge on my honor that I have not given or received any unauthorized assistance on this examination
Your name, printed Your signature

34. This problem concerns the equal loudness curves shown on the right, from an internet reference (not our text). Assume that the Sound Pressure Level is the same as the SIL. The "dashed" curve is the threshold of hearing (0 phons). Give approximate answers, as well as can be read off the curves, but do not worry about exact interpolation between the curves or between the marked SIL or frequency values.

1. These curves were (fiendishly) drawn omitting the intensity scale (in watts/mē) on the right. Supply this scale at at least three levels, knowing that 0 dB corresponds to 10^-12 W/mē
   
2. At what frequency is the ear most sensitive? That is, at what frequency can it hear the lowest intensity of sound?
   

   
   

3. We have a sinusoidal acoustic wave of SIL = 60 dB of variable frequency. The frequency starts out at 20 Hz and slowly increases up to 10,000 Hz.
   1. at what frequency does this wave first become audible?
      

      
      

   2. at what frequency is its loudness level 40 phons?
      

      
      

   3. at what frequency does it appear loudest?
      

      
      

   4. what it its loudness level at this loudest frequency?
      

      
      

4. The loudness level of a 100 Hz tone is 10 phons. What is its SIL?
   

   
   

35. Assume that a person with perfect hearing can hear all frequencies between 200Hz and 20,000Hz equally well. Recall that the Fourier spectum of a square wave contains only odd harmonics, whereas that of a sawtooth wave contains all harmonics. At sufficiently high frequencies, f > f_d, two different wave shapes that sound different at lower frequencies no longer have different tone quality though they are still quite audible.

1. What is a likely reason for this?
   

   
   

2. What do you expect for the approximate value of  f_d when comparing a square wave and a sine wave?
   

   
   

3. What do you expect for the approximate value of  f_d when comparing a square wave and a sawtooth wave?