Making Internet Audio Files for the Macintosh

At the moment this page deals mostly with using a Macintosh computer to record and process sound files. As soon as possible I will do a similar page for the PC using Windows and Windows 95.

I have tried to deal with each part of the process in the order that they would be done if you were starting from the beginning. Where possible I have kept this page free of unnecessary technical terms.

Recording

If you are recording live music or speech I would strongly recommend that you first record the sound onto tape with as good a quality tape recorder and microphone(s) as you have. At this stage the quality of the recording will enhance the definition of the result after you have digitised it, compressed it and whatever else needs doing. Once you have a tape recording that you are completely satisfied with then you can digitise it by recording it onto your computer. This is general advice though, if you have access to a high quality computer based digital recording system (eg. Digidesign Pro Tools) which can be used instead of a tape recorder then that is the obvious equipment to use. To record from tape to computer you will need to make a line connection between the tape recorder and the computer. Use the microphone input on the computer, which on a Macintosh computer is a 3.5 mm stereo jack socket (the same type which is often used for headphones).

There are various pieces of software which run on a Macintosh computer for sound recording. Incidentally all modern Macs have sound input and recording capability though the software which comes with them for recording is rudimentary. There are a number of shareware sound utilities for the Macintosh that you could try. They do extend the capabilities of the computer for sound recording.

Settings

Usually the software will have a default setting for sample size and sample rate, this is often 8 bit 22 KHz. For the purposes of recording for the internet this is an adequate setting. On some equipment though you get better quality using 16 bit 11 KHz as the sample size greatly effects the possible dynamic range of the sample. You should set these basic parameters before recording onto the computer. Whereas, in most cases, deciding on the type of sound file or compression to use is done after recording and before saving the file to disk. The only exception to this in the software that I have included here is SoundHack in which you record straight to disk in a predefined sound file with all parameters set.

Saving the File

The first thing is to decide what type of sound file you want to create. The majority of sound files on the internet are in one of three formats: AIFF, AU and WAVE formats. The file types tend to reflect their origin, AIFF from Macintosh, AU from UNIX and WAVE from Windows. Even so I am fairly sure that most internet daemon applications can play any of these formats regardless of the platform upon which the Browser is running. As the person who is making the sound file the choice of which to use for saving depends upon personal preference. You can only gain knowledge of the differences between the output of the sound files by trying them out. Here is what I have found. Firstly I nearly always use AIFF files and this is mainly because of the number of utilities which make use of these files on the Mac. Where I am less concerned about the quality but have to deal with great differences in volume (speech for instance) then I use an AU file with 8 bit u-law encoding. For the AIFF files I use the lowest sample rate and largest compression ratio that I can whilst still maintaining a satisfactory quality. I nearly always record with just one channel ie. mono. For the general purpose internet sound file I use the following configuration: 8 bit, 22KHz, mono with MACE 3-to-1 compression. If I want the file to be smaller I can either change the sample rate to 11 KHz or use 6-to-1 compression, the results are different but both loose quality. For the very best sound quality with no concern for space I use 16 bit, 44 KHz, stereo with no compression.

Naming Conventions

When naming a sound file you have to be aware of the conventions. Most internet browsers download files first and then launch them using helper or daemon applications. The browser only knows which application to use by the file suffix on the name. This suffix is a full stop followed by some letters. For WAVE files the suffix is .wav, for AIFF .aiff and for AU files .au. Some computers have a limit on the number of letters for the name of a file. The smallest number is 8 letters so it is best to make sure that the name of the file is not longer than that, so for instance you might call an AIFF file of you speaking "myVoice.aiff" (without the quotes).

Linking to the File

Sound files are referenced from a web page in the same way as any other download able file. You can create a hypertext link or image link. This page is not intended to be an instruction on how to write HTML so I won't go into making links in any detail.

Where next?

There are plenty of resources on the internet for sound, and lots of example sound files. You might be interested by RealAudio. It is worth having a look to find out about another type of sound protocol, one which is in the process of evolving specifically for use over the internet. If you are really serious about delivering sound and you want to do lots of recording and processing my main advice is: first look at what shareware is on offer (paying the fees for any that you intend to use) then decide if you want to buy a commercial sound recording and editing package like SoundEdit 16 by MacroMedia or even sound recording hardware for your computer like Digidesign AudioMedia or similar.

Reprinted with permission from author Kris Popat, whose Web site contains good information on utilizing the digital medium.