A microphone responds to changes in air pressure – the waveforms and amplitude that make a sound.
The microphone translates the sound into an electrical output.
- The continuous electrical signal produced by a microphone is an alternating current with a waveform and amplitude thatdirectly correspond to the original acoustic information. If this is captured on a traditional media, such as magnetic tape. When played back it is directly translating the electrical waveform. Electrical Signal Sound-Wave
Digital Information: = Analog-to-Digital Conversion = Any sound before entering into a digital system must be digitized (turned into binary – numerical information). This process is called = Analog-to-Digital Conversion = (or often called - A/D Conversion) Two essential factors affect this process:
Sampling is the process of taking ‘Snap Shots’ of sound at various moments in time.
Playback in succession, these ‘snap-shots’ of sound approximate the original signal.
- Like moving images on a film
The sample Rate is the frequency with which these digital snapshots are collected.
However in order to accumulate to accurate image of the sound there is an important theory to consider...
This process is affected by the ‘SamplingTheory’ or ‘NyquistTheorem’ Each sound cycle MUST be sampled at least TWO times to produce an accurate representation of a frequency. Otherwise will produce false tone and course distortion, this is known as ‘Alias Tones’ So for high frequencies of 20kHz, the sampling must be above 40kHz – 40,000 snapshots a second! As shown on a CD the sample rate is 44.1kHz
A digital system will break down the amplitude into a number of steps - levels of quantization.
Most common found on today's systems are: 8 bit - (8x8) = 64 bit 16 bit – (16x16) = 65,536 24 bit – (24x24) = 16, 777, 216 Though larger ‘Bit Depth records a better sound, take more memory. No matter how good the system still nothing like the real sound. Because it can naturally only behave and register information like a computer. 16 bit / 44.1kHz
Recap Madness: Basic Parameters of Sound: Amplitude = - Since sound is a compression wave, its amplitude corresponds to how much the wave is compressed, the height of the wave, measured in decibels (dB). Wavelength = - Wavelength is the horizontal distance between an exact position on contiguous waves. Frequency/Pitch (Musicians) = - Frequency is the number of wavelengths per second (and/or defined time period), measured in Hertz (Hz), above has 4 cycles
Digital Information: = Analog-to-Digital Conversion Any sound before entering into a digital system must digitizedturned into binary – numerical information. = Analog-to-Digital Conversion = (or often called - A/D Conversion) Two essential factors affect this process: