Chapter 20: Sound

The correct answer is "frequency" because in FM radio, the F stands for the frequency at which the radio waves are transmitted. Frequency refers to the number of complete cycles of a wave that occur in one second. In FM radio, different radio stations are assigned different frequencies, and tuning into a specific frequency allows the listener to receive the corresponding radio station.

The correct answer is "amplitude." In the context of AM radio, the A stands for amplitude. Amplitude refers to the maximum extent of a vibration or oscillation, in this case, the variation in the strength or intensity of the radio waves. AM radio uses amplitude modulation, where the amplitude of the carrier wave is varied to transmit the audio signal.

Sound is produced when an object vibrates, causing the surrounding air particles to vibrate as well. This vibration creates a disturbance that travels through the air as sound waves. Therefore, the source of every sound is something that is vibrating.

Sound waves require a medium to travel through because they are mechanical waves that propagate by vibrating particles in the medium. In a vacuum, there are no particles present to vibrate and transmit the sound waves. Therefore, sound cannot travel in a vacuum.

Sound waves can interfere with each other in a process called destructive interference. This occurs when two sound waves of equal frequency and amplitude meet and their crests align with the troughs of the other wave, resulting in cancellation. When this happens, the sound waves effectively cancel each other out, resulting in no sound being heard. Therefore, the statement that sound waves can interfere with one another so that no sound results is true.

The approximate range of human hearing is 20 hertz to 20,000 hertz. This range is commonly referred to as the audible frequency range. It represents the frequencies at which the average human ear is capable of perceiving sound. Frequencies below 20 hertz are considered infrasound and are typically felt rather than heard. Frequencies above 20,000 hertz are considered ultrasound and are also beyond the range of human hearing. Therefore, the correct answer is 20 hertz to 20,000 hertz.

When we inhale helium, it increases the pitch of our voice because sound travels faster in helium than in air. The speed of sound is determined by the density and elasticity of the medium through which it travels. Helium is less dense than air and has lower molecular weight, which results in faster sound propagation. As a result, when we speak with helium in our lungs, the sound waves travel faster, causing a higher frequency and thus a higher pitch in our voice.

Refraction of sound refers to the change in direction of sound waves as they pass from one medium to another. This phenomenon occurs when sound waves travel through air and encounter a different medium, such as water. The change in the speed of sound in different mediums causes the sound waves to bend or change direction. Therefore, sound can refract in both air and water.

The frequency of a wave refers to the number of cycles or vibrations it completes in one second. In this case, the wave has a frequency of 1000 hertz, which means it completes 1000 cycles per second. Therefore, the correct answer is "1000 cycles per second."

A sound wave is a longitudinal wave because it travels by compressing and expanding the particles of the medium it is passing through in the same direction as the wave itself. In other words, the particles of the medium vibrate back and forth parallel to the direction of the wave propagation. This is different from a transverse wave, where the particles move perpendicular to the direction of the wave. Standing waves and shock waves are not applicable to sound waves.

The speed of sound in air is approximately 340 m/s. The formula to calculate the speed of a wave is speed = frequency x wavelength. In this case, the frequency is given as 340 Hz. By rearranging the formula, we can calculate the wavelength by dividing the speed by the frequency. Therefore, the wavelength of the sound wave is 1 meter.

When two tuning forks with slightly different frequencies are sounded together, they create a beat frequency equal to the difference between their frequencies. In this case, the beat frequency is 246 Hz - 240 Hz = 6 Hz. Therefore, the correct answer is 6 hertz.

A small bell typically has a higher natural frequency compared to larger bells. This is because the natural frequency of an object is determined by its size, shape, and material. Smaller objects tend to vibrate at higher frequencies, while larger objects vibrate at lower frequencies. Therefore, a small bell would have the highest natural frequency among the given options.

Sound travels faster in steel compared to air, water, or a vacuum. This is because sound waves propagate faster in denser mediums, and steel is denser than air, water, or a vacuum. The particles in steel are closer together, allowing sound waves to travel more quickly through the material.

Sound travels faster in warm air because the speed of sound is directly proportional to the temperature of the medium it is traveling through. As the temperature of air increases, the molecules in the air move faster and collide more frequently, allowing sound waves to propagate more quickly. In cold air, the molecules move slower and collide less frequently, resulting in a slower speed of sound.

When a tuning fork is struck, it vibrates and produces sound waves. These sound waves travel through the air or any medium they encounter. When the base of the tuning fork is held against a table top, the vibrations are transmitted to the table, which acts as a resonator. This amplifies the sound waves produced by the tuning fork, making the sound louder. Holding the tuning fork in the air, in shallow water, or in a closed fist does not provide a resonating surface to amplify the sound waves, resulting in a quieter sound.

The correct answer is "pitch." Pitch refers to the perceived frequency of a sound wave. A sound source of high frequency emits a high pitch. Amplitude, on the other hand, relates to the intensity or loudness of a sound, while speed refers to the rate at which sound waves travel. Therefore, the correct answer is pitch, as high frequency corresponds to a high pitch.

The natural frequency of an object refers to the frequency at which it naturally vibrates or oscillates without any external force. This frequency is determined by several factors, including the size, shape, and elasticity of the object. The size of the object affects the wavelength of the vibrations, while the shape determines the mode of vibration. Additionally, the elasticity of the object determines how quickly it can return to its original position after being disturbed. Therefore, all three factors, size, shape, and elasticity, play a role in determining the natural frequency of an object.

Dolphins perceive their environment primarily through the sense of sound. They have excellent hearing abilities and use echolocation to navigate and locate objects in the water. Dolphins emit clicks and listen to the echoes that bounce back, allowing them to create a mental map of their surroundings. While dolphins also have good eyesight, sound is their primary sensory modality for perception.

In a wave, compressions and rarefactions refer to the regions of high and low pressure respectively. When a wave propagates through a medium, the particles in the medium vibrate back and forth in the same direction as the wave. This causes the compressions and rarefactions to also move in the same direction as the wave. Therefore, compressions and rarefactions normally travel in the same direction in a wave.

FM radio waves produce the least static in a radio receiver compared to AM radio waves. This is because FM radio waves have a higher frequency and shorter wavelength, which allows them to carry more information and be less susceptible to interference. On the other hand, AM radio waves have a lower frequency and longer wavelength, making them more prone to static and interference from atmospheric conditions and other electronic devices. Therefore, FM radio provides a clearer and more static-free listening experience.

When tapping the side of a drinking glass with a spoon while filling it with water, the pitch of the sound decreases. This is because as the glass is being filled with water, the space inside the glass decreases. The pitch of the sound is determined by the frequency of the vibrations produced by tapping the glass. As the space inside the glass decreases, the frequency of the vibrations decreases, resulting in a lower pitch sound.

When an object is subjected to forced vibration, it will vibrate with the maximum amplitude at its natural frequency. This is because the natural frequency is the frequency at which the object naturally oscillates with the least amount of energy. When the object is forced to vibrate at its natural frequency, the energy input is efficiently transferred to the object, resulting in maximum vibration. At frequencies below or above the natural frequency, the object will require more energy to vibrate with the same amplitude. Therefore, the least energy required to produce forced vibration in an object occurs at its natural frequency.

When the handle of a tuning fork is held solidly against a table, the sound becomes louder because the table acts as a resonating surface, amplifying the sound waves produced by the fork. However, the time that the fork keeps vibrating becomes shorter because the solid connection with the table allows for efficient transfer of energy from the fork to the table, causing the vibrations to dampen and fade out more quickly.

Sound waves with longer wavelengths have lower frequencies and are able to travel farther in air because they can diffract around obstacles and are less likely to be absorbed or scattered by particles in the air. Shorter wavelengths have higher frequencies and are more easily absorbed and scattered, resulting in shorter travel distances. Ultrasonic waves have frequencies higher than the upper limit of human hearing and are not relevant to this question.

Compressions and rarefactions are characteristic of longitudinal waves. In a longitudinal wave, the particles of the medium vibrate parallel to the direction of wave propagation. Compressions are regions where particles are close together, while rarefactions are regions where particles are spread apart. This type of wave is commonly observed in sound waves, where the particles in the air vibrate back and forth in the same direction as the sound wave travels. Transverse waves, on the other hand, have particles that vibrate perpendicular to the direction of wave propagation.

Sound travels fastest in solids because the particles in solids are closely packed together, allowing sound waves to propagate more efficiently. Ice is a solid, so sound would travel faster in ice compared to water vapor, water, or steam.

When Caruso sang, his voice produced sound waves that matched the natural frequency of the crystal chandelier. This caused the chandelier to vibrate at a high amplitude, eventually leading to its shattering. This phenomenon is known as resonance, where an object vibrates strongly in response to a matching frequency.

The statement "We are best at hearing infrasonic sound" is not true because infrasonic sounds are below the range of human hearing. The statement "We are best at hearing ultrasonic sound" is also not true because ultrasonic sounds are above the range of human hearing. Therefore, the correct answer is "None of the above choices are true" as neither infrasonic nor ultrasonic sounds are within the range of human hearing.

The frequency of the tuning fork is given as 1056 hertz. When the tuning fork and the piano string are struck at the same time, the beats heard are 2 beats/second. This indicates that the frequency of the piano string is slightly different from the tuning fork. When the piano string is tightened slightly, the beats heard increase to 3 beats/second. This suggests that the frequency of the piano string is increasing and getting closer to the frequency of the tuning fork. Therefore, the frequency of the piano string is 1059 hertz, which is the closest option given.

Low frequency sound waves have longer wavelengths and can travel farther in air compared to high frequency sound waves. This is because low frequency waves are less likely to be absorbed or scattered by particles in the air, allowing them to propagate over longer distances. Ultrasonic frequencies, on the other hand, have very short wavelengths and are absorbed quickly by the air, limiting their range. Therefore, the correct answer is low.

The speed of sound in a gas depends on the properties of the gas, such as its density and elasticity. Helium is lighter than neon and has lower density, which allows sound waves to travel faster through it. Therefore, the speed of sound in helium gas is greater than the speed of sound in neon gas.

A base fiddle is louder than a harp because of its sounding board. The sounding board of a musical instrument is responsible for amplifying and projecting the sound produced by the strings. In the case of a base fiddle, the larger size and construction of its sounding board allows for greater resonance and volume, resulting in a louder sound compared to a harp. Thicker strings and lower pitch may contribute to the overall tone and timbre of the instrument, but they are not the primary factors that make the base fiddle louder.

When the frequency of a sound is doubled, it means that the number of complete cycles of the sound wave per second has doubled. As a result, the wavelength, which is the distance between two consecutive points of the wave, will be halved. This is because the speed of sound remains constant in a given medium, so if the frequency increases, the distance between the wave peaks must decrease in order to maintain the same speed. Therefore, doubling the frequency of a sound will halve its wavelength.

Reverberation refers to the persistence of sound in an enclosed space due to multiple reflections. It occurs when sound waves bounce off surfaces and create a series of echoes. This phenomenon is commonly experienced in large rooms or halls with hard surfaces. Therefore, re-echoed sound is the correct answer as it accurately describes the concept of reverberation.

When a piano tuner strikes a key on the piano and a tuning fork at the same time, if the frequency of the key matches the frequency of the tuning fork, there will be no beats heard. This means that the sound waves produced by the piano key and the tuning fork are in perfect harmony and there is no interference between them. Therefore, the correct answer is 0.

The carrier wave has a higher frequency in the case of radio. The carrier wave is the electromagnetic wave that carries the radio signal, while the sound wave represents the audio signal being transmitted. The carrier wave is typically in the radio frequency range, which is much higher than the frequency of the sound wave. Therefore, the carrier wave has a higher frequency compared to the sound wave in radio communication.

Krypton gas has a lower atomic number compared to Xenon gas. In general, the speed of sound in a gas is directly proportional to the square root of the average molecular weight of the gas. Since Xenon gas has a higher atomic number, it has a higher average molecular weight compared to Krypton gas. Therefore, sound travels faster in Krypton gas compared to Xenon gas.

The correct answer is 3. When estimating the distance in kilometers between an observer and a lightning bolt, the general rule is to count the number of seconds between seeing the lightning and hearing it, and then dividing that number by 3. This is because sound travels at approximately 343 meters per second in air, and there are 1000 meters in a kilometer. Therefore, dividing the number of seconds by 3 gives an estimate of the distance in kilometers.

The distance between the explosion and the person is given as 34 km. Since sound travels at a speed of 340 m/s, we can calculate the time it takes for the sound to reach the person by dividing the distance by the speed of sound. In this case, 34 km is equal to 34,000 meters. Dividing this by 340 m/s gives us 100 seconds. Therefore, the correct answer is more than 20 seconds.

An acoustical engineer deals mainly with wave interference when designing a music hall. Wave interference refers to the interaction between two or more waves, resulting in the amplification or cancellation of certain frequencies. In a music hall, it is crucial to control wave interference to ensure optimal sound quality and minimize unwanted echoes or reverberations. By understanding how waves interact and interfere with each other, an acoustical engineer can strategically design the hall's shape, materials, and layout to achieve the desired acoustic properties.

The speed of a sound wave in air depends on the air temperature. This is because the speed of sound is directly proportional to the square root of the temperature. As the temperature increases, the speed of sound also increases. Conversely, as the temperature decreases, the speed of sound decreases. Therefore, the air temperature is a crucial factor in determining the speed of a sound wave in air.

On days when the air nearest the ground is colder than the air higher up, a temperature inversion occurs. This causes sound waves to be refracted downward. This happens because sound travels faster through warmer air and slower through colder air. As the sound waves encounter the colder air near the ground, they slow down and bend downward towards the denser air. This phenomenon is known as downward refraction.

Sound refraction refers to the bending of sound waves as they pass through different mediums with varying densities. This bending occurs because the speed of sound is not constant; it changes depending on the properties of the medium. When sound waves pass from one medium to another, such as from air to water or from warm air to cold air, the speed of sound changes, causing the waves to refract or change direction. Therefore, the correct answer is "variable."

When two sound waves with slightly different frequencies interfere with each other, they produce a phenomenon called beats. The beat frequency is equal to the difference between the frequencies of the two waves. In this case, the wavelengths of the two tuning forks are given, and since frequency is inversely proportional to wavelength, the difference in frequencies can be calculated. By subtracting the smaller wavelength from the larger wavelength, we get a difference of 0.1 meters. Since the speed of sound is approximately 340 meters per second, we can divide the difference in wavelength by the speed of sound to find the beat frequency, which is 0.1/340 = 0.0002941 Hz, approximately 0.3 Hz or 3.0 hertz.

Interference is the correct answer because beats occur when two sound waves of slightly different frequencies interfere with each other. This interference creates a pattern of alternating constructive and destructive interference, resulting in a perceived fluctuation in the loudness of the sound. Refraction and reflection are not related to the occurrence of beats, so they are not the correct answers. Therefore, the correct explanation is that beats result from interference.

When the speed of sound near the ground is greater than it is at higher altitudes, it creates a situation known as a temperature inversion. In this scenario, sound waves tend to bend or refract upwards, away from the ground. This is because the sound waves travel faster in the denser, cooler air near the ground, causing them to refract towards the region of slower speed, which is higher up in the atmosphere. Therefore, the correct answer is upward.

Dolphins use a combination of echoes, the Doppler effect, and ultrasound to perceive their environment. Echoes help them locate objects by bouncing sound waves off them and listening for the returning sound. The Doppler effect allows dolphins to detect the movement of objects by interpreting changes in the frequency of sound waves reflected off them. Ultrasound is used by dolphins for communication and navigation, as it allows them to produce high-frequency sound waves that can travel long distances underwater. Therefore, all of the above choices are correct explanations for how dolphins perceive their environment.

The given options are all types of waves, except for radio waves. Radio waves are electromagnetic waves, while the rest of the options are all types of mechanical waves.

Resonance is a phenomenon where an object oscillates at its natural frequency when subjected to an external force. In this context, resonance is described as forced vibration, meaning that an external force is applied to the object to make it vibrate. The answer "least amount of energy input" suggests that resonance occurs with the minimum amount of energy needed to sustain the vibration at the object's natural frequency. This implies that resonance can be achieved with a relatively small force or energy input.