Using Sounds

The Classic Mac OS, in common with other operating systems, employs sounds that can enhance the user’s experience. Although the author prefers his computer to remain silent, especially when things are going wrong, this can be helpful to some people, especially those with limited eyesight.

• Some computers produce unpleasant clicks, which can be minimised by updating the Mac OS. However, if clicks occur only in specific sound files the problem is probably the actual files. These can be removed by opening the file in a sound utility. You can then either edit out the click or introduce a short fade at the beginning or end of the sound.
• In some instances, audio recording and playback can skip when Virtual Memory (VM) is enabled. If you have this problem just turn off Virtual Memory in the Memory control panel.

The most common sounds on a computer are:-

The Sound Control Panel

The Classic Mac OS contains a Sound control panel for adjusting the sound settings. This is divided into Alerts, Input, Output and Speakers sections, although the Main Volume control is always at the bottom of the window, allowing you to set the overall volume of sound.

• You can silence your machine by setting the Main Volume to its lowest setting or by clicking on the Mute checkbox: any alerts will then cause your menubar to flash.

The most significant sections in the panel are described below.

Alerts

This part of the panel is shown below, with Simple Beep chosen as the alert sound.

• You can duplicate a sound file in the list by dragging its icon to the Desktop.
• Each alert sound is in the form of a system sound file that’s kept inside the System file within the System Folder. To see these files, simply double-click on the System file.
• Some applications also use the alert sounds located in the System file. Unfortunately, programs of this kind don’t always let you disable the sound entirely. To get around this problem, record a short period of silence (unplug the microphone) and name the sound Silence. Now go back to the application and select Silence as your alert sound.

The Alert Volume control is useful, especially on modern machines that can generate alerts and other sounds simultaneously. For example, when using Text-To-Speech (TTS) the volume of a voice is set by the Main Volume control while the alerts are also influenced by the Alert Volume setting.

• Some AV models don’t always play alert sounds properly unless Alert Volume is set at its maximum. You can compensate for this by turning down the Main Volume control.

If you select New Sound you’ll see the following window:-

The function buttons and elapsed seconds counter work in a similar way to those on a real tape recorder. When the recording is complete you can click on Save to store the result.

Input

This part of the panel lets you select one of the available sound input devices, as shown below:-

The most common options are as follows:-

Output

This section of the panel appears as follows:-

Unless your machine has extra audio hardware, the list will only show Built-in, meaning that any sound that your machine makes will go to its sound output socket.

• Older versions of the Mac OS have a Monitors ＆ Sound control panel with options for Sound Output Quality, which is only useful if you want to hear the results of inferior sampling. Most of the time you’ll want full CD-quality, employing the standard sampling rate of 44.1 kHz. In fact, most modern machines only support sampling at this rate.

System and Application Sounds

Appearance Control Panel

This control panel lets you use a particular theme for your computer desktop. It can also make your computer produce a special range of sounds, each one associated with a particular action. These sounds can be enabled by clicking on the Sound tab and choosing a particular set of sounds from the Sound track pop-up menu, as shown below:-

In this case, Apple’s default Platinum Sounds are selected, although other sets can be used.

• The standard set can be modified using ResEdit. First open the Sound Sets folder, inside the Appearance folder inside the System Folder, where you’ll find the file called Platinum Sounds. If you’re proficient with ResEdit you can modify a copy of this file, give it a new name and then select it in the Sound track pop-up menu, as shown above.

SimpleSound

This application, supplied with the Mac OS, can create alert sounds in a similar way to the Sound panel. In addition, it can open sound files that aren’t inside the System file. When you do this, a window appears, showing you the file’s resolution, whether its mono or stereo, its sample rate and duration. To hear the actual sound just double-click in the window.

SimpleSound introduces a slight complication regarding the formats of sound files. The traditional alert sound, as found in the System file, is identified as a sound by the Finder, has a dog-ear on the left-hand side of its file icon and can be heard by double-clicking on the file. However, a SimpleSound document is entirely different, with the dog-ear on the right-hand side. This modern AIFF-C sound file can only be opened in SimpleSound or with the assistance of another sound application.

Sounds in SimpleText

SimpleText, the basic text editor supplied with the Classic Mac OS, can also record sounds and automatically save them in the current text file. To make a recording, select Record in the Sound menu and the standard recording window appears. Once your recording is complete you can recall it by selecting Play. To get rid of the recording, simply select Erase.

Classic Mac OS Sound Resources

The Classic Mac OS can use the resource fork of a file, such as that belonging to an application or other software, to store sounds. These are normally kept as a sound resource, which is identified by a code of snd＜space＞, where ＜space＞ is a space character. This kind of resource was introduced at the time of the Mac II computer and can also be found in documents recognised by the Finder as sound files.

• You can examine the sound resources in a file using Apple’s ResEdit application.
• The size of a sound resource is limited to 16 MB.
• Some applications use other types of resources, such as ASND, GSND, SOUN or wave.

Sound Resource Types

Standard Classic Mac OS sound resources come in two kinds:-

Sound Resources in Detail

The way data is stored in a sound resource depends on the type of sound sample. 8-bit samples are kept as unsigned bytes, as in the data fork of an older FSSD sound file, while 16-bit samples are signed in the same way as in a modern AIFF file. MACE 3:1 or 6:1 compression is optional.

• The Mac OS clipboard stores sounds as an uncompressed Format 1 resource, even when the original material is in a different form, such as a 3:1 compressed Format 2 sound.

In some applications you can edit the header within a sound resource. By modifying this information you can modify the playback sample rate, although the actual sound data remains unchanged. The structure of the header depends on the sound sample itself, as shown by the following table:-

• Sounds pasted from the clipboard receive the minimum header necessary for the sound. For example, an 8-bit mono sound with an extended header gets a standard header. But, a 16-bit sound downsized to 8 bits keeps its extended header. And if an 8-bit sound with a standard header is upsized to 16-bit form an extended header is provided.

©Ray White 2004.