1. PWV. Waves and Vibrations Benchmark 1 Relate characteristics of sounds that we hear to properties of sound waves.

2. What is a Wave? A wave is a moving vibration. Imagine a mass bouncing up and down on a spring. If you were to move the spring and mass as it bounced up and down, you would trace out the path below. The tops of the wave are called the CRESTS and the bottom of the waves are called the TROUGHS. The distance between any two consecutive crests or troughs is the length of the wave called the WAVELENGTH. CRESTS TROUGHS WAVELENGTH

3. WAVE PROPERTIES There are two properties of waves: Amplitude and Frequency Amplitude refers to the “tallness” of a wave, measured from the middle to the top or the middle to the bottom of the wave. AMPLITUDE BIG AMPLITUDE SMALL AMPLITUDE

4. Frequency refers to the number of waves in a given time (or distance). HIGH FREQUENCY LOW FREQUENCY

5. What is Sound? Sound is produced by an object causing vibrations in the air. The vibrations cause the air to vibrate which we hear as sound. Sound is a MECHANICAL WAVE which means that: The wave needs a medium to exist. The speed of the wave is determined by the medium. The MEDIUM is the matter in which the wave travels. Name the medium for the following mechanical waves: Water WavesWater Earth Quake WavesEarth Sound WavesAir – Water - Solids

6. Key concepts Properties SoundPitchLoudness WavesFrequencyAmplitude The two major properties of waves manifest themselves in observable properties of sound:

7. Key concept: Pitch Pitch is an observable property of sound. We associate pitch as a qualitative difference between two sounds. Example: Which has a higher pitch a Flute or a Tuba? Pitch is directly related to the Frequency of a sound wave. A sound wave with a higher pitch has a greater frequency. Flute Which produces sound waves with greater frequency a Flute or a Tuba? Flute

8. Key concept: Loudness Loudness is an observable property of sound. We associate loudness as a qualitative difference between two sounds. Example: Which has greater loundess a Whisper or a Yell? Amplitude is directly related to the Loudness of a sound wave. A sound wave with greater loudness has a larger Amplitude frequency. Yell Which produces sound waves with greater amplitude a Flute or a Tuba? Yell

9. How we Hear Vibrations in the air enter our ear and vibrate the TIMPANIC MEMBRANE (the EARDRUM). The EARDRUM then vibrate the OSSICLES. The OSSICLES cause the liquid in the COCHLEA to vibrate. Little hairs in the liquid vibrate which send signals through the COCHLEAR NERVE to the brain which are interpreted as sound.

10. Web Exploration http://library.thinkquest.org/19537/cgi-bin/showharm.cgi