Sound and Hearing Chapter 17 Section Four

Science Journal Entry 35 Compare and contrast reflection, refraction and diffraction.

Science Journal Entry 36 Explain in detail the doppler effect.

Sound Waves and Speed Sound waves are longitudinal waves. In dry air at 20 o C, the speed of sound is 342 meters per second. Sound waves travel faster in solids than in liquids. Sound waves travel faster in liquids than in gases. Sound waves are longitudinal waves. In dry air at 20 o C, the speed of sound is 342 meters per second. Sound waves travel faster in solids than in liquids. Sound waves travel faster in liquids than in gases. The speed of sound depends on many factors, including density of the medium and how elastic the medium is. The speed of sound depends on many factors, including density of the medium and how elastic the medium is.

Intensity Intensity is the rate at which a wave’s energy flows through a given area. Two factors that intensity depends on, are the wave’s amplitude and the distance from the sound source. Intensity is the rate at which a wave’s energy flows through a given area. Two factors that intensity depends on, are the wave’s amplitude and the distance from the sound source. Sound intensity is measured in decibels (dB). For every 10-decibel increase, the sound intensity increases 10 fold. Sound intensity is measured in decibels (dB). For every 10-decibel increase, the sound intensity increases 10 fold.

Loudness Loudness is a physical response to the intensity of sound. It is subject to a person’s interpretation. Loudness is a physical response to the intensity of sound. It is subject to a person’s interpretation. As intensity increases so does loudness but loudness also depends upon the health of your ears and how your brain interprets the information in sound waves. As intensity increases so does loudness but loudness also depends upon the health of your ears and how your brain interprets the information in sound waves.

Frequency The frequency of a sound wave depends on how fast the source of the sound is vibrating. The frequency of a sound wave depends on how fast the source of the sound is vibrating. By changing the length of tubing through which air moves, instruments produce different frequencies. The trumpet with smaller tubing produces higher frequencies than the French Horn with larger tubing. By changing the length of tubing through which air moves, instruments produce different frequencies. The trumpet with smaller tubing produces higher frequencies than the French Horn with larger tubing.

Frequency of Musical Instruments The air in the tubing forms a standing wave. The longer the tubing, the longer is the wavelength of the standing wave, and the lower is the frequency of the note produced. The air in the tubing forms a standing wave. The longer the tubing, the longer is the wavelength of the standing wave, and the lower is the frequency of the note produced.

Pitch Pitch is the frequency of a sound as you perceive it. Although high- frequency sounds have a higher pitch and low-frequency sounds have a low pitch, it depends on your age and the health of your ears how you perceive it. Pitch is the frequency of a sound as you perceive it. Although high- frequency sounds have a higher pitch and low-frequency sounds have a low pitch, it depends on your age and the health of your ears how you perceive it.

Frequency and Hearing Most people hear sounds between 20 hertz and 20,000 hertz in frequency. Most people hear sounds between 20 hertz and 20,000 hertz in frequency. The sounds that are too low for most people to hear are called infrasounds. The sounds that are too low for most people to hear are called infrasounds. The sounds that are too high for most people to hear are called ultrasounds. The sounds that are too high for most people to hear are called ultrasounds.

Ultrasound and Sonar Ultrasound pulses of short duration 1/8000 th of a second, are sent into a patient and the computer software uses the reflected pulses to make a detailed map of structures and organs inside of the body. Ultrasound pulses of short duration 1/8000 th of a second, are sent into a patient and the computer software uses the reflected pulses to make a detailed map of structures and organs inside of the body. Sonar also uses ultrasound to determine the distance of objects under water. Sonar stands for sound navigation and ranging. Sonar also uses ultrasound to determine the distance of objects under water. Sonar stands for sound navigation and ranging.

Sonar The distance to an object is calculated using the speed of sound in water and the time that the sound wave takes to reach an object and the echo takes to return. The distance to an object is calculated using the speed of sound in water and the time that the sound wave takes to reach an object and the echo takes to return.

What is the Doppler Effect? Discovered by Christian Doppler, the Doppler Effect is a change in sound frequency caused by motion of the sound source, motion of the listener, or both. Discovered by Christian Doppler, the Doppler Effect is a change in sound frequency caused by motion of the sound source, motion of the listener, or both. An observer hears a higher frequency, when the object producing the sound is moving toward them and as the sound source moves away, the observer hears a lower frequency. An observer hears a higher frequency, when the object producing the sound is moving toward them and as the sound source moves away, the observer hears a lower frequency.

Coming and Going Sounds

Compressed or Expanded Sound Waves

The Ear The ear consists of three main sections. The outer ear gathers and focuses sound into the middle ear. The middle ear receives the sound and amplifies the vibrations. The inner ear uses nerve endings to sense vibrations and send signals to the brain. The ear consists of three main sections. The outer ear gathers and focuses sound into the middle ear. The middle ear receives the sound and amplifies the vibrations. The inner ear uses nerve endings to sense vibrations and send signals to the brain.

Vibrating Drums The eardrum in the outer ear vibrates at the same frequency as the sound waves striking it. The eardrum in the outer ear vibrates at the same frequency as the sound waves striking it. A drum skin vibrates up and down sending a series of compressions and rarefactions through the air. A drum skin vibrates up and down sending a series of compressions and rarefactions through the air. A large bass drum is better at producing low frequency sounds but a small bongo drum would produce higher frequencies better. A large bass drum is better at producing low frequency sounds but a small bongo drum would produce higher frequencies better.

How Sound is Reproduced Sound is recorded by converting sound waves into electronic signals that can be processes and stored. Sound is recorded by converting sound waves into electronic signals that can be processes and stored. Sound is reproduced by converting these electronic signals back into sound waves. Sound is reproduced by converting these electronic signals back into sound waves. Electronic sound must be converted back into sound waves by loudspeakers. Electronic sound must be converted back into sound waves by loudspeakers.

Microphones In a microphone, the sound of a singer’s voice causes a membrane in the microphone to vibrate which causes a magnet to vibrate which will turn sound waves into electronic signals. In a microphone, the sound of a singer’s voice causes a membrane in the microphone to vibrate which causes a magnet to vibrate which will turn sound waves into electronic signals. Loudspeakers make these signals sound waves again so everyone can hear. Loudspeakers make these signals sound waves again so everyone can hear.

Loudspeakers A loudspeaker picks up the electronic signals that it receives from a microphone or sound board. A loudspeaker picks up the electronic signals that it receives from a microphone or sound board. The electronic signals cause a magnet attached to a membrane to vibrate. The vibrating membrane sends sound waves through the air. The electronic signals cause a magnet attached to a membrane to vibrate. The vibrating membrane sends sound waves through the air.

Music Most musical instruments vary pitch by changing the frequency of standing waves. Most musical instruments vary pitch by changing the frequency of standing waves. Resonance is often used to amplify sound in musical instruments. Resonance is the response of a standing wave to another wave of the same frequency. Resonance is often used to amplify sound in musical instruments. Resonance is the response of a standing wave to another wave of the same frequency.

Acoustic Engineering Large concert halls are designed to prevent dead spots from destructive interference. Large concert halls are designed to prevent dead spots from destructive interference. The Central Michigan University Music Building has sound absorbing tiles on the sides and rear of the hall. The Central Michigan University Music Building has sound absorbing tiles on the sides and rear of the hall. The curved reflecting panels above the stage help gather and direct sound waves toward the audience. The curved reflecting panels above the stage help gather and direct sound waves toward the audience.

Conclusion The properties of speed, intensity, loudness and pitch explain the behaviors of sound waves. The properties of speed, intensity, loudness and pitch explain the behaviors of sound waves. Sound waves are used not only for hearing but also for medical ultrasound and for Sonar. Sound waves are used not only for hearing but also for medical ultrasound and for Sonar. The Doppler Effect explains why a person hears a higher pitch from a approaching sound source and a lower pitch when the sound source is moving away. The Doppler Effect explains why a person hears a higher pitch from a approaching sound source and a lower pitch when the sound source is moving away.