1. Properties of Sound

2. Loudness Loudness describes your perception of the energy of sound – It describes what you hear The closer you are to the sound, the louder it is Loudness of a sound depends on two things: – 1. The amount of energy it takes to make the sound – 2. The distance from the source of the sound

3. Energy of a Sound Source The greater the energy used to make a sound, the louder the sound – Example: Playing a guitar When you use more energy to pull the strings of the guitar the louder the noise produced by the guitar is The more energy you use, the larger the amplitude The larger the amplitude produces a louder sound

4. Distance From a Sound Source Loudness increases the closer you are to a sound source – Close to the sound source, the sound waves cover a small area – As waves travel away from the sound source, it covers more area The total energy of the wave stays the same whether it’s close to the source or far away from it – The closer the sound wave is to its source, the more energy it has in a given area

5. Distance From a Sound Source The amount of energy a sound wave carries per second through a unit area is its Intensity A sound wave of greater intensity sounds louder When you move away from the sound source, loudness decreases, because the intensity decreases

6. Measuring Loudness Loudness is measured using the unit called the decibel (db) Each 10-db increase in loudness represents a tenfold increase in the intensity of the sound – Example: soft music at 30-db sounds 10x louder than a 20-db whisper Soft music at 30-db sounds 100x louder than a 10-db sound of rustling leaves Sounds louder than 100-db can cause damage to your ears, especially if you listen to those sounds for long periods of time

8. Pitch Pitch is a description of how high or low the sounds seems to a person The pitch of a sound that you hear depends on the frequency of the sound wave

9. Pitch and Frequency Sound waves with a high frequency have a high pitch and sound waves with a low frequency have a low pitch Most people can hear sound with frequencies between 20Hz and 20,000Hz – Sound waves with frequencies above the normal human range of hearing are called ultrasound – Sound waves with frequencies below the normal human range of hearing are called infrasound – People cannot hear infrasound or ultrasound waves

10. Changing Pitch Lungs: Air From the lungs rushes up the trachea Vocal Cords: which are located in your voice box, or larynx vibrate as air rushes pass them Sound: Sound waves produced by the vibrating vocal cords come out through the mouth