Unfortunately, explaining this subject even in basic terms requires some techno babble. I guess after reading this you will either want more detailed information or you will be reaching for the headache tablets and going for a lie down!
If you are just trying to understand the best format to use for your project I guess understanding the reason behind the sound is less important than the result. If you fall into this camp you may want to quickly read this article, listen to the examples at the end of the article and then experiment with some audio files.
CD Quality Audio – Uncompressed.
The technical bit!
In order to reproduce a digital sound accurately many measurements of that sound are required and need to be stored as digital information (0’s and 1’s). Simplistically speaking, the more measurements or samples taken per second of a sound, the higher the quality that can be reproduced.
It is generally considered that CDs reproduce high quality audio, a quality of 44.1kHz 16bit.
This means audio is sampled 44100 times per second at a bit rate of 16. Bit rate refers to the quantisation or in simple terms the accuracy of each measurement taken. For example, leaving the standard of the CD for a moment, if you were to listen to something sampled at 8 bit it world sound grainy as the low accuracy of the samples would produce audible distortion. Going the other way, 24 bit would sound finer than a CD at 16 bit as the sampling accuracies are higher.
Anyway back to the CD, the size of a music file is quite large, however, this is fine as the CD has much storage space relatively speaking. The capacity of an audio CD is up to 80 minutes of CD quality audio (44.1 Khz, 16 bit)
CD audio, as you would buy in a shop and play on your CD player is known as uncompressed audio. Uncompressed formats are AIFF (mac), WAV (PC) and CDDA (CD Audio)
Pure uncompressed audio is great to listen to, however, high quality means large file size! Whilst this is fine on your CD player it is impractical for online use or for use on many of the popular portable media devices such as the ipod.
For this reason, compressed audio formats are used. A compressed format uses code that removes unnecessary information from the audio making the file size many times smaller than uncompressed audio files. There are a number of different compressed file formats, some better than others. The basic principle is that the information about sounds that cannot be heard (sounds obscured by others) is removed to save space.
Probably the most common compressed format is mp3. There are numerous others including WMA, AAC, Ogg vorbis and Real Audio.
A good quality mp3 is about 10% of the size of the comparative CD audio file. MP3 converters enable you to adjust the quality to suit the file size you require. With MP3 it is the bit rate that controls the file size and the auible quality. As MP3s are much smaller than CDDA files the bit rate is measured in kbps.
Generally speaking, If you want a small file size you can save it as a low quality audio file. High quality audio mp3s mean a larger file size. See our chart and examples below.
Format and Size VS Download speed.
So what does this mean to our ears, our storage space and our download speeds? Generally, small file sizes equal poor audio quality but quick download speed, whereas high quality audio means bigger files and a slower download time. The chart gives some examples of download speeds. You can also see how long they take to fully download into the flash player.
Sound quality is subjective so it is worth experimenting with different file sizes in order to see which is most suited to your purpose.
Have a listen to our MP3 examples, see if you can hear the difference. Whether you can hear any diiference will depend on how good your ears are and how good your speakers are.
It is common practice to make larger files such as WAVs smaller in order to use them in streaming web media and numerous other multimedia projects. This involves converting them into compressed files such as mp3s and there is plenty of software out there that will do the job, however, I can personally recommend DB Power amp It is easy to use and free although there is a small license fee for MP3 conversion.
As a rule of thumb, it is never good practice to turn a compressed file back into an uncompressed format. Once the compression process removes information it can never be added back into the file. Also, it is not worth making a low quality MP3 into a higher quality one, the same principle applies.
The audio examples are on Media Music Now – Click Here >