Chapter One: An Acoustics Primer
5. What is frequency? | page 3
Frequency is directly related to wavelength, often represented by the Greek lambda (
). The wavelength is the distance in space required to complete a full cycle of a frequency. The wavelength of a sound is the inverse of its frequency. The formula is:
wavelength ( ) = speed of sound/frequency
Flash wavelength example here
| Example: A440 Hz (the frequency many orchestras tune to) in a dry, sea level, 68°F room would create a waveform that is ~2.5 ft. long (2.56 = 1128 (feet/sec) / 440). Be certain to measure the speed of sound and wavelength in the same units. Notice how if the speed of sound changed due to temperature, altitude, humidity or conducting medium, so too would the wavelength. |
As can be seen from the above formula, lower frequencies have longer wavelengths. We are able to hear lower frequencies around a corner because the longer wavelengths refract or bend more easily around objects than do shorter ones. Longer wavelengths are harder for us to directionally locate, which is why you can put your Surround Sound subwoofer most anywhere in a room except perhaps underneath you. At 20°C, sound waves in the human hearing spectrum have wavelengths from 0.0172 m (0.68 inches) to 17.2 meters (56.4 feet).
For further study, see Hyperphysics->Periodic Motion
