Sound Representation
Explore the fundamentals of sound as pressure waves and learn how analog signals are converted to digital signals through sampling and quantization. Understand key concepts such as frequency, wavelength, bit depth, and the Nyquist-Shannon sampling theorem to comprehend how computers represent sound digitally and reconstruct it accurately.
What is sound?
Sound is a pressure wave or a longitudinal wave that travels through the air with compressions and rarefactions. Compressions are the regions with higher air pressure, whereas rarefactions are the regions with lower air pressure.
Sound is propagating from left to right in Figure 1.
Frequency is a measure of how rapidly a signal changes, whereas, the wavelength of a waveform, is the reciprocal of its frequency. More rapid changes in a signal imply higher frequency and shorter wavelength.
Analogue signals
An analogue wave is a continuous signal that measures the change in amplitude over time. Fundamentally, anything measured is an analogue quantity, including the human voice, the brightness of an image, a thermometer reading, light sensors, air pressure, etc. The analogue signal can be represented as a sine wave, as shown in Figure 2.
Digital signals
A digital signal is a discrete-time, quantized amplitude ...
