ch26_tb

Chapter 26: Sound ** 2 6.1 Origin of Sound ** All sounds are made by the vibrations of material objects.

Vibrating Strings: piano, violin, guitar


Vibrating Vocal Chords: your voice


The original vibration stimulates the vibration of a larger or more massive material...  >> the sounding board of a stringed instrument, the air column within a reed or a wind instrument, or the air in the throat and mouth of a singer.)  ...This vibrating material then sends a disturbance through a surrounding medium (usually air) in the form of Longitudinal Waves. The frequency of the vibrating source = the frequency of sound waves produced.
 * (Some examples of materials that are often stimulated:

//Pitch// – How we describe our subjective impression about the frequency High Pitched Sound = Hight Vibration Frequency Low Pitched Sound = Low Vibration Frequency

//Infrasonic// – Sound waves with frequencies below 20 hertz //Ultrasonic// – Sound waves with frequencies above 20,000 hertz Young can usually hear pitches with frequencies from 20 to 20,000

Comression- The pulse of compressed air
 * 26.2 Sound in Air

Rarefaction- A disturbance in air (or matter) in which the pressure is lowered. Opposite of compression.

26.3 Media That Transmit Sound

26.4 Speed of Sound

26.5 Loudness

26.6 Forced Vibration

Forced Vibration- The vibration of an object that is made to vibrate by another vibrating object that is nearby. The sounding board in a musical instrument amplifies the sound through forced vibration.

26.7 Natural Frequency

Natural Frequency- A frequency at which an elastic object, once energized, will vibrate. Minimum energy is required to continue vibration at that frequency. Also called resonant frequency.

26.8 Resonance

Resonance- A phenomenon that occurs when the frequency of forced vibrations on an object matches the object's natural frequency, and a dramatic increase in amplitude results.

26.9 Interference

26.10 Beats**
 * Beats** – The periodic variation in the loudness of sound.