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Audio Basics : Page 3

This section provides some basic background information for adding sound to your site.


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Basic Sound Concepts
When you start looking into putting audio on your Web site, and maybe purchase an audio editor, you're going to be hit with a zillion new terms. This section defines basic sound terminology and concepts.

Acoustic Pertaining to sound and the act of hearing.
Analog Sound Refers to sound signals and energy, i.e., what you hear.
Bit Bits and Kilobits are units of measurement for data transfer. A bit stands for "binary digit," and it's the smallest unit of computer data. Bits consist of 1's and 0's. Most audio files on the net have been recorded at a resolution of 8 or 16 bits. 16 bit is CD standard, but 8-bit is more useful for the Web because it's smaller size equals less download time. The resolution bit rate determines the overall dynamic range of the output from an audio source. Each bit of resolution contributes approximately 6 decibels.
Decibel Decibel, or Db, is a measure of the ears response to sound. or Db, is a unit to express relative difference in power, usually related to electrical or sound signals.
Digital Sound When you put sound on your computer, the sound signals need to be transformed into a "language" that your computer can understand. Computers read sound signals once they're in a binary code—a whole bunch of 0s and 1s. Binary code sound signals are known as digital signals.
Dynamic Range A measure of the span between the quietest and the loudest sounds.
Resolution The resolution refers to how many locations represent the waveform at each given sample. Think about what resolution means to your images—the more resolution, the better your image looks. It works the same way with audio files. Resolution is measured in terms of bps, or bits per second. Resolution equals the number of bits allocated for each sample or output value.
Sampling An ADC (Analog to Digital converter) is a computer chip that's used to convert analog signals into digital information. This process is called sampling.

After you've converted sound to digital information, you can "view" this sound, in a graphic representation (looks like part of an EKG) with a sound editor program. You can slice this information, dice it, reverse the sound, do the "Alvin and the Chipmunks" effect by speeding up the sound, cut off as much of the waveform as you'd like, loop it and a whole bunch of other fun editing techniques. Digital signals need to be converted back to analog in order to hear them. TD>

Sample Rate When editing sound you need to determine the sampling period or rate and the bit resolution. The sampling rate refers to the number of samples (or "bits" of sound) per second. The more samples per second, the better it sounds. The most common sample rates are 44.1k (which means 44,100 samples per second), 22.05k and 11k (actually 11,025). The ear is very picky. It requires an extraordinary amount of audio "samples" to hear a sound clip. The engineers who designed CDs decided that 44,100 'samples' per second is what the ear needs to hear sounds accurately.


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