All PHYS 1270 Exams
Which of the following is not one of the ossicles in the middle ear of humans?
B) sagmus (saddle)
Two pitches separated by an octave have a pitch interval of
1200 ₵
A standing wave of the third overtone (n=4) is excited in a closed pipe, 1.2 m long. The speed of sound is 343 m/s. The number of pressure antinodes in the standing wave pattern is:
4
A resonance tube can be excited at frequencies of 500, 750, and 1000 Hz but at no others between 400 and 1100 Hz. Is it open or closed, and how long is it? Assume the speed of sound in air is 343 m/s
500 = 2 x 250 750 = 3 x 250 1000 = 4 x 250 → all harmonics of fundamental = 250 Hz → open pipe f1 = v/2L → L = v/2 f1 = (343 m/s)/ [2 x 250 Hz)] A) Open with a length of 0.69 m
Which of the following is a definition for the term consonant?
A basic speech sound in which the breath is at least partly obstructed
Vocal folds oscillate at the frequency they do because of
A) their length. B) the external tension they experience. C) the internal tension they exert. D) their density.
A sound wave resonates in a tube with both ends open. What are the wavelengths of the three lowest resonating frequencies generated in the tube?
B) 2L, L, 2L/3
Several types of reeds, including the double reeds of the woodwinds, the lip reeds of brass instruments, and the vocal folds, rely on the Bernoulli principle to help them vibrate. How does this happen?
As high velocity air enters the mouthpiece, the pressure in that region reduces and pulls the reed closed.
A tuning fork with a frequency of 440 Hz is played simultaneously with a fork with a frequency of 436 Hz. What is the beat frequency that is heard?
Beat frequency = | f2 - f1 | f-beat = |440 Hz - 436 Hz| f-beat = 4 Hz
A chorus of 343 people each singing at the sample loudness will sound how much louder than one (1) of them performing as a soloist?
C) The chorus will sound seven times (7x) louder than the soloist. Cubed sqrt(Number of people playing)
Which of the following is an accurate statement?
Displacement nodes and pressure antinodes occur at the same place in an organ pipe
Train A and Train B are approaching each other on the same track. Train A is instructed to pull onto a side track to allow train B to pass. The frequency of the horn on each train is set to 1000 Hz. As train B is approaching, the engineer gives a greeting "toot" of his horn. What frequency does the engineer in Train A hear as he sits at rest on the side track?
Doppler Shift problem: As source approaches, wave fronts are closer together, making a shorter observed wavelength A) He hears a "toot" with f slightly greater than 1000 Hz.
A soprano saxophone and a clarinet are about the same size and are both single reed instruments. Why are the sounds produced by the soprano saxophone and the clarinet so different?
E) The clarinet has a cylindrical bore and the saxophone has a conical bore, so they have different harmonic recipes.
The sound of a piano playing very softly yields a sound intensity level of 55 dB. What is the intensity of the sound?
I = I_threshold ∙ 10^(SIL/10 dB) I = (10^-12 W/m2) ∙ 3.1 x 10^5 = 3.1 x 10^(5-12) W/m^2 I = 3.1 x 10^-7 W/m^2
A bugler playing "Taps" that is I = 1 x10-4 W/m2 at 10 m. What will be the intensity 100 m away?
I2 / I1 = (r1/ r2) I2 = (1 x10^-4 W/m^2) ∙ (10 m/100 m)^2 I2 = 1 x10^-6 W/m^2
Why are wind instruments "warmed up" before a performance?
If not warmed, they will play flat (have a lower frequency) because the speed of sound is lower in room temperature air than in the air from the player's lungs
Where would you find the vocal folds?
Layrnx
Frequency spectrum with major peaks at 436 Hz, 872 Hz, 1309, and 1745 Hz Look at the vibration recipe (frequency spectrum) above. What wind instrument below could not have produced this sound?
Looks like a full harmonic series but All but clarinets have a full harmonic series Clarinet (closed-ended, cylindrical pipe)
If you blow fast moving air over the top of a sheet of paper, how do you expect the pressures to compare on the top and bottom of the sheet and how do you expect the paper to move?
Lower pressure on top and higher pressure on bottom, so the paper moves up Bernoulli Effect: Higher speed, lower pressure
A lady weighs 450 N and wears stiletto shoes. The area of the stiletto heel is 1 x 10-4 m2 . What is the pressure the lady exerts by standing on one stiletto heel?
P = (450 N) / (1 x 10-4 m2) P = 4.5 x 106 Pa
A sound wave has a frequency of 240 Hz. The air temperature is 20o C. Find the period of the sound
P = 1/f = 1/ (240 Hz) = 0.004 s
If the repeat period for a complex sound is 15 sec, what is its fundamental frequency?
P repeat = 1/f f = 1/ P repeat = 1 / (15 s) = 0.067 s
Which of the following tuning schemes is based on each scale step being
Pythagorean tuning
A 1000 Hz sound wave has an intensity of 0.005 W/m2 What is the Sound Intensity Level (SIL) in dB for this sound?
SIL = 10 dB ∙ Log( I / I threshold ) SIL = 10 dB ∙ Log [(0.005 W/m2)/ (10^-12 W/m2) SIL = 10 dB ∙ (9.7) = 97 dB
The lowest detectable intensity (the threshold of hearing, I threshold) is 1x10 -12 W/m2. What is the Sound Intensity Level for the threshold of hearing?
SIL = 10 dB ∙ Log( I / I threshold ) SIL = 10 dB ∙ Log [(1x10 -12 W/m2)/ (10-12 W/m2)] SIL = 0 dB
A singer is outdoors, on level ground, with no reflecting structures nearby. About how many dB difference in sound intensity level would you expect between the front and back rows of an audience, located between 40-m and 10-m away from the singer?
SIL2 - SIL1 = -20 dB ∙ Log (r2/r1) SIL2 - SIL1 = -20 dB ∙ Log (40/10) SIL2 - SIL1 = -20 dB ∙ 0.6 = -12 dB
Without the computer running, the background sound level in my office is measured to be 40 dB. When I turn on the computer system, the sound level in the office is found to be 50 dB. What is the ratio of the intensity with the computer on to that when the computer is off?
SIL2 - SIL1 = 10 dB ∙ Log (I2/I1) 50 dB - 40 dB = 10dB ∙ Log (I2/I1) 10 dB = 10 dB ∙ Log (I2/I1) 1 = Log (I2/I1) → 10^1 = I2/I1 B) 10^1:1
A glass window is installed in the window space and the intensity level of the sound entering through the window is reduced from 84 dB to 70 dB. The ratio of the open window intensity to the glasses-in window intensity is:
SIL2 - SIL1 = 10 dB ∙ Log (I2/I1) 84 dB - 70 dB = 10dB ∙ Log (I2/I1) 1.4 = Log (I2/I1) → 10^1.4 = I2/I1 = 25
If one violin produces a reading of 70 dB on your sound level meter, what reading should you get for four violins playing together under the same conditions? Assume that the violins play with equal intensities
SIL4 violins - SIL1 violin = 10 dB ∙ Log (4I1/I1) SIL4 violins - 70 dB = 10dB ∙ Log (4) SIL4 violins = 70 dB + 10dB ∙ (0.6) SIL4 violins = 70 dB + 6dB = 76 dB
) A room is 10-m x 10-m with a ceiling 10-m high. The floor is covered with padded carpet (α = 0.5) and the ceiling with acoustical plaster (α = 0.6). The rest is gypsum wall board (α = 0.04). What is the 60 dB reverberation time for the room?
Se = α floor carpet * S floor + α ceiling * S ceiling + α wall * S walls = 0.5 x 100 m2 + 0.6 x 100 m2 + 0.04 x 400 m2 = (50 + 60 + 16) m2 = 126 m2 TR = 0.16 ∙ volume/Se = (0.16 x 1000)/126 = 160/126 = 1.27 s
Which of the following statements about Loudness Level is false?
The Loudness Level is an objective measurement.
A clarinet is basically sealed at one end (you blow into a very narrow hole), but open at the other. A flute is essentially open at both ends. If you have a clarinet and flute of equal lengths, and play the fundamental, which of the following statements is true?
The clarinet will sound lower than the flute and the clarinet's harmonic recipe will contain only odd harmonics
Reflections happen at open holes along the pipe of a woodwind. What effect does an open hole have on the standing waves in the pipe?
The effective length of the pipe is shortened
You have constructed a Helmholtz oscillator for an experiment from a glass flask, half filled with water. What happens when you pour out half of the water in the flask?
The frequency gets lower because the "air spring" is less stiff with more volume
The speed of sound on a humid day is faster than on a day with low humidity. If a pipe organ is designed to play in a region with low humidity, what will happen to the fundamental tone produced by that same pipe organ on a rainy, humid day?
The pitch will go up
Which of the following accurately defines 'diffraction'?
The spreading out of the wave around an obstacle, or the spreading out of a wave as it goes through a slit.
A violinist plucks the A-string by pulling it 0.005 m to the left with a force of 8 N in 0.001 s. How much work was done by the violinist?
W = (8 N) (0.005 m) W = 0.04 J
Falsetto is:
a register of the vocal folds.
Compared to a 200 Hz sound, a 300 Hz sound traveling in the same medium would have:
a shorter wavelength and the same speed.
When a bowed instrument is played properly, the bow causes a string to vibrate by:
alternately sticking to and slipping over the string, while moving perpendicular to the string
Humans are most sensitive to sounds:
at frequencies from 2000 Hz to 5000 Hz.
A wave with a frequency of 14 Hz is traveling from left to right across a rope as shown in the diagram below. Positions A and B in the diagram are separated by a horizontal distance of 48 cm. Positions C and D in the diagram are separated by a vertical distance of 12 cm
c) 24 cm
Which of the following describes the cochlea?
coiled, fluid-filled tube, carries waves and converts waves into nerve impulses
The vocal folds of the human voice:
create a sound with a complex harmonic recipe and are not responsive to the standing waves in the vocal tract.
If you hear the thunder five seconds after you see the flash of lightning, how far away was the lightning strike?
d = (343 m/s) (5 sec) d = 1715 m
Hooke's Law relates the:
distance a spring stretches to the force applied to the spring.
A transverse wave is observed to be moving along a lengthy rope. Adjacent crests are positioned 2.4 m apart. Exactly six crests are observed to move past a given point along the medium in 12 seconds. Determine the speed of these waves
f = # wavelengths/sec = (6 crests) / (12sec) = 1.2 m/s
A mass m = 0.50 kg hangs from a spring with a constant k = 350 N/ m. With what frequency will the mass oscillate?
f = (1/2π) [k/m]^1/2 f = (1/2π) [700]^1/2 = (1/2π) (26.5 Hz) f = 4.2 Hz
A sound wave travelling in air has a wavelength of 1.6 x10-2 m. If the velocity of sound is 320 m/s, calculate the frequency of sound
f = v/λ = (320 m/s) / (1.6 x 10^-2 m) c) 2 x 10^4 Hz
The A2 key two octaves below "Middle C" on the piano produces a sound wave with a wavelength of 3.12 meters. The speed of sound in air at room temperature is 343 m/s. What is the frequency of the sound waves associated with the A2 key?
f = v/λ = (343 m/s) / (3.12 m) f = 110 Hz
A piano string of length L = 2 m has a linear mass density μ = 0.05 kg/m. What tension must be applied to the string for its fundamental frequency to be 40 Hz?
f1 = (1/2L) x (T/μ)^1/2 f1^2 = (1/2L)^2 x (T/μ) T = 1280N
What gap must a flautist provide with a jet velocity of 15 m/s to produce an edge tone of 330 Hz?
f_edge = 0.2 v_Jet/b b = 0.2 v_Jet / f_edge b = 0.2 (15 m/s) / (330 Hz) = 0.01 m
The 'pitch' of a musical note is normally given in terms of its:
frequency
Resonance occurs when a force causes an object to vibrate at which of the following?
its natural frequency
Sound in air can best be described as a
longitudinal wave of air compression and rarefaction
Which of the following defines the term fundamental frequency?
lowest resonant frequency of a vibrating object
A sound wave is differs from a light wave in that a sound wave is:
not capable of traveling through a vacuum
Which property of a sound wave could change, and we would not be able to hear a difference?
phase
Operatic singers alter the shapes of their vocal tracts to:
produce more sound from high frequency harmonics of the vocal folds.
The property of waves that accounts for the reverberation of a concert hall is:
reflection
Marching soldiers are commanded to break steps when they are crossing a long bridge. When soldiers march in unison it produces a sound of the same frequency and large energy. If this frequency matches with the natural frequency of the bridge then it will cause _______ and the bridge will vibrate with large amplitude.
resonance
The critical bandwidth is:
the maximum difference in frequency between two simultaneous tones that are not distinguishable
The frequency of a wave is:
the number of cycles in a second
With equal temperament tuning,
the pitch interval is the same for each semitone in the chromatic scale
The sound of a flute is different to, say, a clarinet playing the same note because:
they produce different harmonic recipes.
A sound wave has a frequency of 1200 Hz as it travels in air temperature that is 30o C. What is the speed of sound for this sound?
v = [343 + 0.6(30-20)] m/s v = 349 m/s
Humpback whales are known to produce a collection of elaborate and repeating sounds with frequencies ranging from 20 Hz to 10 kHz. The sound waves travel through water at speeds of approximately 1400 m/s. Determine the wavelength of the 20 Hz waves.
v = f λ λ = v/f = (1400 m/s)/ (20 Hz) λ = 70 m
Determine the length of guitar string required to produce a fundamental frequency (1st harmonic) of 256 Hz. The speed of waves in a particular guitar string is known to be 405 m/s
v = f λ λ = v/f = (405 m/s) / (256 Hz) = 1.58 m For the fundamental on a string, L = ½ λ = ½ (1.58 m) λ = 0.79 m
The lowest pitch that the average human can hear has a frequency of 20,000 Hz. If sound with this frequency travels through 20o C air, what is its wavelength?
λ = v/f = (343 m/s)/ (20,000 Hz) λ = 0.017 m
