Sound Chapter Summary

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Questions and Answers

What characteristic of sound distinguishes loud and faint sounds?

  • Loudness (correct)
  • Frequency
  • Timbre
  • Pitch

Which phenomenon demonstrates that sound behaves like a wave?

  • Interference
  • Absorption
  • Refraction (correct)
  • Deflection

The relationship between loudness and intensity of sound is best described by which of the following equations?

  • L = K log I (correct)
  • L = K/I
  • L = I^2
  • L = K * I

In a longitudinal wave, how do the particles of the medium move?

<p>Back and forth along the wave direction (A)</p> Signup and view all the answers

What factor does NOT affect the loudness of sound?

<p>Frequency of sound (D)</p> Signup and view all the answers

What occurs when air is pumped out of a jar, affecting the sound of a bell?

<p>Sound becomes weaker (C)</p> Signup and view all the answers

Which of the following concepts describes the energy passing through a unit area perpendicular to the sound wave?

<p>Intensity (C)</p> Signup and view all the answers

Which of the following is NOT a characteristic of sound waves?

<p>Conduction (B)</p> Signup and view all the answers

What is the relationship between frequency and pitch?

<p>Frequency is directly proportional to pitch. (B)</p> Signup and view all the answers

What unit is used to measure intensity level of sound?

<p>Bel (C)</p> Signup and view all the answers

What happens to the wavelength when the pitch of sound increases?

<p>Wavelength decreases. (C)</p> Signup and view all the answers

Which statement is true regarding the effect of amplitude on loudness?

<p>Increased amplitude leads to increased loudness. (B)</p> Signup and view all the answers

What is the audible frequency range for the human ear?

<p>20Hz to 20,000Hz (C)</p> Signup and view all the answers

How does sound behave when it reflects off a surface?

<p>It produces an echo. (C)</p> Signup and view all the answers

Why do we use a logarithmic scale to measure sound intensity?

<p>Because loudness is directly proportional to the logarithm of intensity. (B)</p> Signup and view all the answers

What effect does an increase in frequency have on the amplitude of a wave?

<p>The amplitude remains unchanged. (B)</p> Signup and view all the answers

What is the primary characteristic that defines noise?

<p>Irregular and sudden vibrations (A)</p> Signup and view all the answers

What negative health effects can noise cause?

<p>Hearing loss and aggression (D)</p> Signup and view all the answers

How does soft porous material contribute to noise reduction?

<p>It absorbs sound energy (A)</p> Signup and view all the answers

Why is communication through tin cans with a string more effective than shouting?

<p>Sound spreads more in air, causing loss of clarity (B)</p> Signup and view all the answers

What role does diffraction play in sound perception around obstacles?

<p>It enables sound waves to bend around corners (A)</p> Signup and view all the answers

What is an example of a medical application of ultrasound?

<p>Removing blood clots in arteries (A)</p> Signup and view all the answers

Why is it challenging to hear someone clearly in a room with overly absorbent surfaces?

<p>It interferes with sound reflection needed for clarity (D)</p> Signup and view all the answers

What property of sound allows us to identify individuals based on their voice?

<p>Quality of sound (B)</p> Signup and view all the answers

Why must the volume of a stereo in a carpeted room be tuned higher than in a room with a wooden floor?

<p>Wooden floors create maximum sound reflection, reducing volume. (B), Carpeted rooms absorb more sound energy. (C)</p> Signup and view all the answers

How do speed and frequency of a wave differ?

<p>Speed is how fast waves move; frequency is how often they occur. (B), Speed is affected by the medium, frequency is not. (C)</p> Signup and view all the answers

What factor causes two listeners to perceive different loudness levels of the same music?

<p>Variations in individual hearing sensitivity. (C), The acoustics of the room. (D)</p> Signup and view all the answers

Is there a difference between echo and reflection of sound?

<p>There is no difference; both refer to the same phenomenon. (B), Echoes are sound reflections heard later. (D)</p> Signup and view all the answers

Why can two separate 50dB sounds not be added to make 100dB?

<p>The dB scale is determined by intensity ratios. (B), Adding decibel levels requires a logarithmic calculation. (D)</p> Signup and view all the answers

What is the main benefit of using ultrasound in the medical field?

<p>It replaces the need for surgery. (A), It helps visualize internal organs and tissues. (C)</p> Signup and view all the answers

What is the unit of sound intensity?

<p>Bel (A), Watts per meter squared (C)</p> Signup and view all the answers

Which of the following statements is true regarding the intensity level of sound at 3.0×10−6 Wm−2?

<p>It exceeds the intensity of faintest sound. (B), It corresponds to a decibel level lower than 100 dB. (D)</p> Signup and view all the answers

What is the depth of the sea if the speed of sound in seawater is 1500 ms−1 and the time for echo is 1.5 seconds?

<p>1125 m (B)</p> Signup and view all the answers

How far is the cliff from a person who hears an echo after 5 seconds if the speed of sound is 346 ms−1?

<p>865 m (A)</p> Signup and view all the answers

What depth is determined if ultrasound returns from the seabed after 3.42 seconds with a speed of 1531 ms−1?

<p>2618 m (B)</p> Signup and view all the answers

What is the wavelength of a sound at 20,000 Hz with the speed of sound at 343 ms−1?

<p>0.01715 m (A)</p> Signup and view all the answers

What is the wavelength of a sound wave with a frequency of 20 Hz and a speed of 343 ms−1?

<p>17.15 m (C)</p> Signup and view all the answers

If a sound wave has a frequency of 2 kHz and travels a distance of 1.5 km, how long would it take to cover this distance?

<p>10 seconds (C)</p> Signup and view all the answers

What is the distance traveled by sound in air in 2.5 seconds, if the speed of sound is 343 ms−1?

<p>857.5 m (C)</p> Signup and view all the answers

If the speed of ultrasound in seawater is 1531 ms−1, how far would it reach in 3.42 seconds?

<p>5236 m (A)</p> Signup and view all the answers

What is the intensity level of normal conversation in decibels?

<p>64.8 dB (A)</p> Signup and view all the answers

When the sound intensity level is at 80 dB, what is the intensity of the sound?

<p>$10^{-4}$ Wm−2 (C)</p> Signup and view all the answers

How is the frequency of a sound wave calculated given the speed of sound and its wavelength?

<p>Frequency = Speed / Wavelength (B)</p> Signup and view all the answers

What is the frequency of a sound with a speed of 330 ms−1 and a wavelength of 0.05 m?

<p>660 Hz (B)</p> Signup and view all the answers

What is the period of heartbeats if the frequency is 1.2 Hz?

<p>0.83 s (D)</p> Signup and view all the answers

When a marine survey ship receives an echo after 1.5 s, what is implied about the time taken for the sound to travel to the seabed and back?

<p>0.75 s each way (D)</p> Signup and view all the answers

What is the mathematical representation for sound intensity in decibels?

<p>$10 \log_{10}(I/Io)$ (D)</p> Signup and view all the answers

Which of these frequencies falls within the audible range of the human ear?

<p>10000 Hz (B), 20000 Hz (C), 2000 Hz (D)</p> Signup and view all the answers

Flashcards

Intensity Level of Sound

The difference between the loudness of an unknown sound and a reference sound.

Unit of Intensity Level

Bel (a larger unit) or decibel (a smaller unit).

Frequency

The number of sound waves passing a point per second.

Pitch

How high or low a sound is; related to frequency.

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Amplitude and Loudness

Greater amplitude = louder sound.

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Frequency and Pitch Relationship

Higher frequency = higher pitch.

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Echo

Sound reflected from a surface.

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Human Hearing Range

20 Hz to 20,000 Hz.

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Longitudinal wave

A wave where particles of the medium move back and forth along the direction of wave propagation.

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Sound wave propagation

Sound needs a medium (like air) to travel. Without a medium, sound cannot propagate.

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Sound as a wave

Sound exhibits wave-like properties such as reflection, refraction, and diffraction.

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Sound intensity

Sound energy passing per second through a unit area perpendicular to the sound wave.

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Loudness

Sound's perceived strength or volume; subjective measure of sound intensity.

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Loudness vs. Intensity

Loudness is a subjective measure related to intensity but also factors like the amplitude and distance from the source. Intensity is an objective measure of sound energy.

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Factors affecting loudness

Loudness depends on the amplitude (strength) of the vibrating object, the area of the vibrating object, and distance from the source.

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Intensity level unit

Decibel (dB) is the unit used to measure the intensity level or volume of sound.

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Noise definition

Unpleasant sounds that can negatively affect human health and cause accidents. Noise is characterized by irregular and sudden vibrations.

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Acoustic Protection

Methods to reduce noise pollution using materials that absorb or reflect sound.

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Sound absorption by materials

Soft, porous materials absorb sound energy, reducing echoes and softening noises.

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Sound reflection

Sound bounces off rigid and smooth surfaces more prominently.

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Ultrasound medical uses

Ultrasonic waves used for diagnosing and treating medical conditions, including removing blood clots and imaging the thyroid.

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Sound transmission in solids vs. air

Sound travels significantly faster in solids compared to air, leading to clearer communication.

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Sound quality and recognition

We recognize individuals by their unique sound qualities, even with similar loudness.

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Diffraction and sound vs light

Sound waves diffract (bend) more than light waves, which explains why we can hear around corners but not see.

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Sound Reflection vs. Echo

Sound bouncing off a surface is called reflection, and if that reflected sound is heard distinctly after some time delay, it's an echo.

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Loudness & Listener

Loudness depends on both the sound's intensity and the listener's ear sensitivity.

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Speed vs. Frequency

Speed measures how fast a wave travels, while frequency counts how many waves pass a point per unit time. They are different quantities.

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Decibel Scale Non-Linear

Adding decibel values isn't arithmetic. A 50dB sound plus another 50dB sound is NOT a 100dB sound.

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Sound Intensity Unit

The unit of sound intensity is Watts per square meter (Wm−2).

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Sound Intensity Level (dB)

The intensity level of a sound is a logarithmic scale (using base 10 logarithm) expressed in decibels (dB).

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Sound intensity = 3.0×10-6 Wm-2

This represents a normal conversation in terms of sound energy per area

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Decibel level of normal conversation

The intensity level of a normal conversation, calculated using the formula 10 log(I/Io), where I is the intensity of sound and Io is the intensity of the faintest sound.

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Frequency (Hz)

The number of waves that pass a given point per unit time.

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Period (s)

The time it takes for one complete cycle of a wave.

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Audible range

The range of frequencies that human ears can detect.

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Wave speed (m/s)

The rate at which a wave travels through a medium

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Heart rate frequency

The number of heartbeats per unit of time (e.g., beats per minute).

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Speed of sound in seawater

The speed at which sound travels through seawater, typically around 1500 meters per second.

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How to calculate the depth of the sea?

Use the speed of sound in water and the time it takes for an echo to return to determine the depth.

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Sound wave wavelength

The distance between two consecutive peaks or troughs of a sound wave.

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Relationship between frequency and wavelength

Higher frequency sound waves have shorter wavelengths. Lower frequency sound waves have longer wavelengths.

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Speed of sound in air

The speed at which sound travels through air, usually around 343 meters per second at 20 degrees Celsius.

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How long does sound take to travel?

Calculate the travel time by dividing the distance by the speed of sound.

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Study Notes

Sound Chapter Summary

  • Sound is a longitudinal wave, meaning particles vibrate parallel to the direction of the wave's travel.
  • Sound needs a medium to travel (like air, water, or solids), unlike light.
  • Sound travels faster in denser mediums (like solids) than less dense mediums (like gases).
  • The loudness of a sound is related to its amplitude. Higher amplitude corresponds to louder sound.
  • Pitch is related to frequency. Higher frequency corresponds to a higher pitch sound.
  • Sound's speed depends on the medium and temperature.
  • Sound can be reflected, refracted, and diffracted.
  • Echo is the reflection of sound waves.
  • The human ear can detect sounds with frequencies between 20Hz and 20,000Hz (also called audible range).
  • An intensity level is measured in decibels (dB).
  • Ultrasound has frequencies above 20,000Hz.
  • The intensity of sound (measured in Wm⁻²) decreases as distance from the source increases.

Review Questions

  • For sound production: Vibrating objects create vibrations in the surrounding medium, transmitting sound.
  • Effect of medium on speed: Sound travels faster in solids, then liquids, then gases, due to differences in the density of the mediums and how quickly vibrations are passed between molecules.
  • Longitudinal nature of sound: Sound propagates by compressions and rarefactions of particles. Vibrations move back-and-forth along the direction of the wave's travel.
  • Sound as a wave: Sound exhibits properties of waves, including reflection, refraction, and diffraction.
  • Loudness vs. Intensity: Loudness is a subjective measure of how loud a sound seems, while intensity is a physical measure of the energy in the sound wave. These are related but not identical.
  • Frequency vs. Pitch: Frequency is the number of waves per second, while pitch is how high or low we perceive a sound to be (subjective). Pitch increases with frequency.
  • Amplitude vs. Loudness: Amplitude is the maximum displacement of a particle from its equilibrium position in a sound wave, loudness is a subjective measure of the sound's energy and strength to the listener.

Additional Concepts

  • Intensity level: A logarithmic scale to describe the range of sound intensities we can hear.
  • Audible range of sound: The range of frequencies humans can hear (typically 20Hz to 20,000Hz)
  • Decibel scale: A logarithmic scale used to quantify the intensity of sound, used for measuring its loudness. A common reference level is the intensity of the faintest audible sound.
  • Uses of ultrasound: Ultrasound is used in medicine for imaging and other applications because of its high frequency that allows for better resolution than many other types of sound waves.
  • Echo: The bouncing back of sound waves when they encounter a surface.

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