What is a sound Sound is a pressure

What is a sound? • Sound is a pressure wave in air or any other material medium. • The human ear and brain working together are very good at detecting and decoding patterns of information in sound (e. g. , speech and music)

Sound in Air:

Sound in Air:

Sound in Air:

Sound in Air:

Sound in Air:

Sound in Air:

How do things make sounds? • Vocal Cords vibrate air by vibrating back and forth as air is exhaled.

How do things make sounds? • Vocal Cords vibrate air by vibrating back and forth as air is exhaled.

How do things make sounds? • Pianos “hammers” hit strings inside the piano vibrating them back and forth.

How do things make sounds? • String Instruments vibrate air when the string vibrates back and forth when plucked or bowed.

How do things make sounds? • Drums vibrate back and forth when struck with a hand or stick.

Characteristics of Sound: • Frequency – the more waves per second a sound has, the higher the pitch • High Frequency High Note • Low Frequency Low Note

Characteristics of Sound: • Amplitude - the taller the waves, the louder the sound • Low Amplitude Soft Sound • High Amplitude Loud Sound

Characteristics of Sound: • The speed of sound in air is constant • The speed of sound in air 343 m/s • Most humans can hear frequencies between 20 Hz and 20 000 Hz • Wavelength is from 0. 0017 meters and 17 meters.

Wave Characteristics: f = frequency λ = wavelength v = speed units: Hz (Hertz) units: m (meters) units: m/s v=f∙λ f=v÷λ λ=v÷f

A sound wave has a wavelength of 0. 2 meters. What is its frequency in Hz? Given λ = 0. 2 m v = 343 m/s Unknown Equation f=? f=v÷λ Solution f=v÷λ f = 343 ÷ 0. 2 f = 1715 Hz Scientific Units

A sound wave has a frequency of 600 Hz. What is its wavelength in meters? Given v = 343 m/s f = 600 Hz Unknown Equation λ=? λ=v÷f Solution λ=v÷f λ = 343 ÷ 600 λ = 0. 57 m Scientific Units