Sound Properties of Sound Sound waves are longitudinal

Sound

Properties of Sound �Sound waves are longitudinal! �Sound can be explained by understanding: ◦ Speed ◦ Intensity and loudness ◦ Frequency and pitch �Most people hear sound between the frequency of 20 Hz and 20, 000 Hz.

Anatomy of Sound �External Ear: ◦ Focus the sound into the ear canal. �Middle Ear: ◦ Amplifies the vibrations. �Inner Ear: ◦ Senses the vibrations and signals the brain.

Anatomy of Sound �The Middle Ear is made up of 3 tiny bones known as the hammer (malleus), anvil (incus) and stirrup (stapes).

A. Speed �The speed of sound (in dry air at 20°C) is 342 m/s. �The speed of sound varies with the temperature and phase of matter it is traveling through. ◦ Most fast is solids ◦ slowest in gases

B. Intensity and Loudness �Intensity refers to the rate at which sound waves travel in a given area. ◦ Depends upon the amplitude of the sound waves and the distance from the source. �Loudness is a subjective term. It is the physical response to sound intensity. Depends upon a person’s health, age, etc.

B. Intensity and Loudness �Intensity is measured in Bels (decibels, d. B). The scale is more logarithmic ◦ 0 d. B can barely be heard. ◦ 20 d. B is 100 times more power than 0 d. B.

C. Frequency and Pitch �Sound frequency depends upon how fast the source of the sound is vibrating. ◦ Longer waves produce lower sounds frequency ◦ Shorter waves produce high frequency �Pitch is a person’s perception of sounds frequency. (Subjective) ◦ High pitch = high frequency ◦ Low pitch = low frequency

Ultrasound �Ultrasound waves are used in medicine and sonar techniques. �Ultrasound can be used to construct images of internal structures.

D. The Doppler Effect �The Doppler Effect explains how the pitch of a sound can change as it passes a person or point. �It is the change in sounds frequency caused by motion of the sounds source, motion of the listener, or both.

�As a sound source approaches the frequency increases. As the source moves away the frequency drops.