# Lecture in Sound | Giancoli Physics

(Last Updated On: March 21, 2020)

### Lesson Objectives – the students should be able to:

• Determine the speed of sound in air at one atmosphere of pressure at different temperatures.
• Distinguish between the following terms: pitch, frequency, wavelength, sound intensity, loudness.
• Determine intensity level in decibels of a sound if the intensity of the sound is given in W/m2.
• Explain how a standing wave can be produced in a wind instrument open at both ends or closed at one end and calculate the frequencies produced by different harmonics of pipes of a given length.
• Determine the beat frequency produced by two tuning forks of different frequencies.
• Explain how an interference pattern can be produced by two sources of sound of the same wavelength separated by a distance d.
• Solve problems involving two sources for m, d, λ, and the angular separation (θ) when the other quantities are given.
• Solve for the frequency of the sound heard by a listener and the wavelength of the sound between a source and the listener when the frequency of the sound produced by the source and the velocity of both the source and the listener are given.
• Explain how a shock wave can be produced and what is meant by the term “sonic boom.”

### Summary of Chapter 12

• Sound is a longitudinal wave in a medium.
• The pitch of the sound depends on the frequency.
• The loudness of the sound depends on the intensity and also on the sensitivity of the ear.
• The strings on stringed instruments produce a fundamental tone whose wavelength is twice the length of the string; there are also various harmonics present.
• Wind instruments have a vibrating column of air when played. If the tube is open, the fundamental is twice its length; if it is closed the fundamental is four times the tube length.
• Sound waves exhibit interference; if two sounds are at slightly different frequencies they produce beats.
• The Doppler effect is the shift in frequency of a sound due to motion of the source or the observer.

### Units of Chapter 12 – Keywords

• Characteristics of Sound
• Intensity of Sound: Decibels
• The Ear and Its Response; Loudness
• Sources of Sound: Vibrating Strings and Air Columns
• Quality of Sound, and Noise; Superposition
• Interference of Sound Waves; Beats
• Doppler Effect
• Shock Waves and the Sonic Boom
• Applications: Sonar, Ultrasound, and Medical Imaging