Tutorial 3

Q3) List the steps you would go through to record, edit, and process a set of sound files for inclusion on a web site. How would you digitally process the files to ensure they are consistent, have minimum file size, and sound their best?

Digital audio is created when you represent the characteristics of a sound wave using numbers—a process referred to as digitizing. You can digitize sound from a microphone, a synthesizer, existing recordings, live radio and television broadcasts, and popular CD and DVDs. In fact, you can digitizesounds from any natural or prerecorded source. 

Digital audio data is the actual representation of a sound, stored in the form of thousands of individual samples that represent the amplitude (or loudness) of a sound at a discrete point in time. How often the samples are taken is the sampling rate. The three sampling frequencies most often used in multimedia are CD-quality 44.1 kHz (kilohertz), 22.05 kHz, and 11.025 kHz. 

Digital audio is not device dependent, and sounds the same every time it is played. For this reason digital audio is used far more frequently than MIDI data for multimedia sound tracks. 

Sound can be digitized from any source, live or prerecorded. The amount of information stored about each sample is the sample size and is determined by the number of bits used to describe the amplitude of the sound wave when the sample is taken. Sample sizes are either 8 bits or 16 bits. The value of each sample is rounded off to the nearest integer (quantization). 

The steps and considerations to record and edit digital audio are:

è The file size (in bytes) of a digital recording is sampling rate * duration of recording in seconds * (bit resolution / 8) * number of tracks (1 for mono, 2 for stereo).
è Consumer-grade audio compact disc are recorded in stereo at a sampling rate 44.1 kHz and a 16-nit resolution. Other sampling rates include 22.05 and 11 kHz, at either 16 or 18 bits.
è When recording (digitizing) audio, it's important to keep the recording level near the maximum without going over it.
è Important steps in digital sound editing include removing blank space from the star and end of a recording and normalizing the sound to bring all clips to approximately the same level.
è  The native sound file formats for most Macintosh sound editing software are the SND and AIF formats, and most editing software is a WAV file.
è  Many audio editors provide tools such as resampling, fade-ins and -outs, equalization, time stretching, various digital signal processing effects, and reversing sounds.