1. INTRODUCING SOUND WAVES Ritchel Dyan Z. Bagayas

2. The Nature of Sound  Sound travels in waves as it moves through the air or some other medium (substance)  Waves are produced by a vibrating object.  As a vibrating object moves outward, it compresses the surrounding medium, producing a region of compression called a condensation.  As the vibrating object then moves inward, the medium expands into the space formerly occupied by the object. This region of expansion is called a rarefaction.

4.  Sound waves consist of these condensations and rarefactions.  Sound waves must travel through a medium.  Sound is called a longitudinal wave because the vibrations are in the same direction as the motion and speed of the wave.  It travels at a speed of 331 m/s in air at 0 o C.  The speed increases, at a rate of 0.6 m/s per Celsius degree.  If something moves faster than sound, it is said to be supersonic. If it travels at the speed of sound, it travels at Mach 1; three times the speed of the sound is called Mach 3.

5.  Acoustics is the science of sound and of its effects on people.  Condensation is a region of compression in a sound wave.  Frequency of sound waves refers to the number of condensation or rarefactions produced by a vibrating object each second.  Decibel is the unit used to measure the intensity level of a sound. A 3000-hertz tone of zero decibels is the weakest sound that the normal human can hear.  Hertz is the unit used to measure frequency. One hertz equals one cycle (vibration) per second.  *Other terms used in the study of sound can be found in page 451.

6.  The nature of a particular sound can be described in terms of  Frequency and Pitch  Intensity and loudness and  Quality

7. Frequency and Pitch  Pitch is related to its frequency. Higher frequency means higher pitch.  Frequencies of sound waves humans can hear range from about 20-20,000 hertz or cycles per second.  The loudness of sound is related to the wave’s energy or intensity.  As the frequency of sound waves increases, the wavelength decreases. Wavelength is the distance between any point on one wave and the corresponding point on the next one.