What is Sound?
Simply put, sound is the vibration of air molecules. More technically, sound is the detection of the vibration of air molecules by our ears.
Sound is measured in two ways
- Frequency
- Frequency is the speed at which the air molecules vibrate. On a sine wave of sound, it is the distance between the peaks.
- It is measured in Hertz (Hz), cycles of vibration per second.
- Human can hear from about 50 Hz (low) to 15,000 Hz (high).
- Elephants can hear lower frequency sounds while dogs and bats can hear higher frequency sounds.
- This is also known as the pitch of the sound.
- High frequency is high pitched, e.g. a flute, piccolo, high-hat cymbal.
- Low frequency is low pitched, e.g. a bass, bass drum.
- Amplitude
- Amplitude is the volume or loudness of the sound. On a sine wave, it is the height of the wave.
- It is measured in decibels (dB).
Resources
- Oscilloscope and Sounds. Use this to see how the keys of a piano produce different sound waves.
- Virtual Oscilloscope. Use this to adjust the frequency and amplitude of a sound sine wave to hear what happens.
- Chrome Music Lab. Fun, interactive sound apps.
How is Sound Digitized?
Put simply, the amplitude of sound wave is measured at very short intervals of time. The amplitude is a decibel number which is stored as a binary number. It is taken often 44,000 times per second. So, sound is digitized as 44,000 binary decibel recordings every second. Sound files are in the Megabyte range because there are millions of numbers recorded every minute.
