Sound Recorder for Mac
Sound Recorder is an intuitive and user-friendly Mac OS X application that enables you to record the audio emissions from your line-in device or built-in microphone. Keep in mind, however, that Sound Recorder was created before QuickTime gained the audio recording feature in version 7, so you would better use QuckTime instead if it's version 7 or newer. Also, it uses old APIs, so it's not a recommended choice.
The application features a simple and intuitive user interface displaying a main window and a Settings window. From the main window, you can start / stop or pause / continue the recording process, or access the Settings.
Sound Recorder does not come empty handed, as it offers quite a few custom options. You can select one of the compression types, the volume and the gain of the recording via the Compression tab of the Settings window.
Furthermore, you can also select the sample rate, size (8bit or 16bit) and use (mono or stereo) by accessing the Sample tab.
Finally, Sound Recorder providers a Source tab in its preferences to select the audio source you want to capture. Two options are given: the Built-in Input (Line In) and the Built-In Microphone (Internal Microphone).
As soon as you've finished recording, you can immediately listen to it using a built-in audio player. You can also use this player to export the recording to various formats such as AVI, 3G, Apple TV, MPEG, AIFF and many more.
In the light of what's been said, Sound Recorder is not a great choice if you want to just record sounds from your built-in microphone, since newer versions of QuickTime already include this feature. However, you can still use it if you're using older operating systems.