Basic unit of Sound?

Question

If we consider computer graphics to be the art of image synthesis where the basic unit is a pixel.

What is the basic unit of sound synthesis?

[This relates to programming as I want to generate this via a computer program.]

Thanks!

Answer 1

frequency and amplitude of the wave are what make up sound. That is for a tone. Music or for that matter most noise is a composite of multiple simultaneous sound waves superimposed on one another.

• The unit for amplitute is the Bel. (We use tenths of a Bel therefore the term decibel)
• The unit for frequency is the Hertz.

That being said synthesis of music is a large field.

Answer 2

The byte, or word, depending on the bit-depth of the sound.

Answer 3

The basic unit is a sample

In a WAVE file, the sample is just an integer specifying where to move the speaker head to.

The sample rate determines how often a new sample is fed to the speakers (I'm not entirely sure how this part works, but it does get converted to an analog signal first). The samples are typically laid out in the file one right after another.

When you plot all the samples with x-axis being time and y-axis being sample_value, you can see the waveform.

In a wave file, samples can (theoretically) be any bit-size from 0-65535, which remains constant throughout the wave file. But typically 16 or 24 bits are used.

Answer 4

Sound can be expressed as several different units, but the most common in synthesis/computer music is decibels (dB), which are a relative logarithmic measure of amplitude. Specifically they are normally relative to the maximum amplitude of the audio system.

When measuring sound in "real life", the units are normally A-weighted Decibels or dB(A).

The frequency of a sound (i.e. its pitch) is its amplitude over time, or in the digital world, its amplitude over samples. The number of samples per unit of real time is called the sampling rate; conventional hi-fi systems have sampling rates of 44 kHz (44,000 samples per second) and synthesis/recording software usually supports up to 96 kHz.

Everything sound in the digital domain can be represented as a waveform with the X-axis representing the time (or sample number) and the Y-axis representing the amplitude.

Answer 5

Bitmapped graphics are based on sampling the amplitude of light in a 2D space, where each sample is digitized to a given bit depth and often converted to a logarithmic representation at a different bit depth. The samples are always positive, since you can't be darker than pure black. Each of these samples is called a pixel.

Sound recording is most often based on sampling the magnitude of sound pressure at a microphone, where the samples are taken at constant time intervals. These samples can be positive or negative with respect to perfect silence. Most often these samples are not converted to a logarithm, even though sound is perceived in a logarithmic fashion just as light is. There is no special term to refer to these samples as there is with pixels.

The Bels and Decibels mentioned by others are useful in the context of measuring peak or average sound levels. They are not used to describe the individual sound samples.

You might also find it useful to know how sound file formats compare to image file formats. WAVE is an uncompressed format specific to Windows and is analogous to BMP. MP3 is a lossy compression analogous to JPEG. FLAC is a lossless compression analogous to 24-bit PNG.