Chapter 14: Sound and Hearing
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Chapter 14: Sound and Hearing

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Questions and Answers

What factor primarily determines the loudness of a sound?

  • The amplitude of the sound wave (correct)
  • The frequency of the sound wave
  • The distance from the sound source (correct)
  • The duration of the sound

    • How does temperature affect the speed of sound in air?

  • Speed of sound is independent of air composition
  • Speed of sound increases as temperature increases (correct)
  • Higher temperatures decrease the speed of sound
  • The speed of sound is constant regardless of temperature

    • Which phenomenon describes the change in frequency of sound due to the motion of the source or observer?

  • Doppler Effect (correct)
  • Refraction
  • Interference
  • Reflection

    • What is a sonic boom?

    <p>The sound associated with a shock wave from an object traveling faster than the speed of sound</p> Signup and view all the answers

    Which of the following is NOT a condition for standing waves to form?

    <p>The amplitude must be different</p> Signup and view all the answers

    What phenomenon occurs when an object travels through air at speeds greater than Mach 1?

    <p>A sonic boom</p> Signup and view all the answers

    At approximately what speed is Mach 1 defined at sea level under room temperature conditions?

    <p>1,225 km/h</p> Signup and view all the answers

    In the context of standing waves in a tube open at one end, where does maximum particle movement occur?

    <p>At the open end</p> Signup and view all the answers

    What generates a sonic boom?

    <p>The compression of air waves by an approaching object</p> Signup and view all the answers

    In harmonics, which equation represents the fundamental frequency for a tube open at both ends?

    <p>f = nv / 2L</p> Signup and view all the answers

    What would increase the overall sound intensity level in an open tube?

    <p>Increasing tension within the tube</p> Signup and view all the answers

    What is the primary characteristic of timbre in a sound wave?

    <p>Sound quality</p> Signup and view all the answers

    When sound waves merge into a single shock wave, what is the result at the speed of sound?

    <p>A sonic boom</p> Signup and view all the answers

    What is the frequency of the first harmonic for a pipe that is 2.46 m long and open at both ends, given the speed of sound is 343 m/s?

    <p>69.7 Hz</p> Signup and view all the answers

    If a piano string has a beat frequency of 4 Hz when compared to a tuning fork vibrating at 440 Hz, what are the possible frequencies of the piano string?

    <p>436 Hz or 444 Hz</p> Signup and view all the answers

    How does the frequency of a sound change when the source is moving towards the observer, according to the Doppler effect?

    <p>It increases.</p> Signup and view all the answers

    What phenomenon occurs when a source of sound moves faster than the speed of sound?

    <p>Sonic Boom</p> Signup and view all the answers

    What happens to the wavelength of a wave when its frequency increases while the speed of sound remains constant?

    <p>The wavelength decreases.</p> Signup and view all the answers

    In a standing wave formed in a closed pipe, what is the location of the nodes?

    <p>Only at the closed end</p> Signup and view all the answers

    If the smallest air-column length at which a resonance peak occurs is 9.00 cm for a pipe closed at one end, what is the second smallest length for resonance?

    <p>18.0 cm</p> Signup and view all the answers

    In a scenario where a piano tuner moves towards the piano, leading to a dropped beat frequency from 4 Hz to 2 Hz, what can be inferred about the piano note's frequency?

    <p>It decreases with the tuner's approach.</p> Signup and view all the answers

    Study Notes

    Chapter 14: Sound and Hearing

    • Sound is a disturbance of matter transmitted outward from its source.
    • Sound waves are longitudinal waves consisting of alternating compressions and rarefactions.
    • Frequency of a sound, f, is the number of complete waves passing a point per unit time (measured in Hz).
    • Wavelength, λ, is the distance between two consecutive compressions or rarefactions.
    • The speed of sound, v, is the rate at which the wave travels. The relationship is: v = λf .
    • The speed of sound depends on the medium and its temperature.
    • Sound travels faster in solids than in liquids and faster in them than in gases, and faster at higher temperatures in all states of matter.
    • Humans can hear frequencies ranging from 20 Hz to 20,000 Hz.

    What is Sound?

    • A vibrating tuning fork creates a series of compressions and rarefactions in the air.
    • The crests of the wave correspond to compressions, the troughs to rarefactions.
    • A vibrating source transfers energy to surrounding molecules.
    • This energy is used to compress and expand the surrounding medium.
    • High pressure regions are called compressions, low pressure regions are called rarefactions.

    Loudness & Intensity

    • Loudness is related to the energy of the source and the distance.
    • Loudness is proportional to intensity, which is power per unit area (W/m²).
    • Intensity of a point source varies inversely with the square of the distance from the source.
    • The measurement of loudness, or intensity level is in decibels (dB).

    Speed of Sound

    • The speed of sound is usually given as dependent on the temperature and type of medium.
    • The speed of sound at sea level is approximately 331 m/s at 0° Celsius (273 Kelvin)
    • The formula is: v = λf.
    • Speed of sound is approximately independent of frequency.

    Threshold of Hearing & Pain

    • Threshold of hearing: The faintest sound a human can hear (0 decibels).
      The intensity is 1x10-12 W/m².
    • Threshold of pain: The loudest sound a human can tolerate without causing pain (approximately 120–130 dB). Intensity is approximately 1 W/m².

    Intensity vs Loudness

    • Human perception of loudness is logarithmic, not linear.
    • One important logarithmic scale is decibels (dB).
    • A 10dB change corresponds to a change in intensity by a factor of 10 (e.g. from 20dB to 30dB).

    Doppler Effect

    • A change in the observed frequency of a sound due to the motion of the source and/or observer.
    • The frequency observed by a stationary observer increases as the source approaches and decreases as it moves away.

    Standing Waves

    • When waves of equal frequency and amplitude travel in opposite directions, standing waves are created.
    • Sound waves from a source may interfere with reflected waves, producing standing waves.
    • The amplitude of the vertical oscillation of any element of the string depends on the horizontal position of the element.
    • The wavelength of the fundamental standing wave in a string fixed at both ends is twice the length of the string.
    • A standing wave in a tube open at one end has one antinode at the open end and a node at the other end.
    • A standing wave in a tube open at both ends has antinodes at both ends.

    Beats

    • Beats are an interference pattern that results from the superposition of two sound waves with slightly different frequencies.
    • The beat frequency is the difference between the frequencies of the two interfering waves.

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    Description

    Explore the fascinating world of sound in this quiz on Chapter 14. Learn about sound waves, frequency, wavelength, and how sound travels through different media. Test your understanding of the basic principles of sound and hearing.

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