Copying a recording: The best way to make a copy of a recording for enhancement is to digitize the original recording directly into a computer. That is to say, to process the original recording through equipment that turns the recording into a series of numbers in a computer. If this is done properly, it causes no harm to the original recording. Then the expert can work with the numbers in the computer that represent the sounds. It is important to make copies through electrical connections between recorders or between the recorder and the computer rather than by putting the microphone of one recorder next to the speaker of another, which will introduce excessive distortion.

Acoustic filters: The tools most often used by in acoustic restoration are acoustic filters, which are devices or computer programs that let some sounds pass through unimpeded, while causing others to stay behind. You can think of them as being like coffee filters that allow the liquid coffee to pass, while keeping the unwanted grounds behind. Similarly, an acoustic filter can allow speech sounds to pass through while holding back noise.

Exhibit for the jury: I usually prepare an exhibit of the enhanced recording, in which the words or other sounds of interest are separated from the rest of the recording, and can be repeated a number of times. This exhibit can be played to the jury so they can hear the evidence for themselves.