Recorder: We recommend use of a high-quality digital audio recorder that can produce WAVE files directly. There are three current possibilities:

1. Most laptop computers can function as digital audio recorders. All you need is an external microphone and some recording software. For Mac, we recommend Amadeus Pro. For Windows, you can use CDEX.

2. In terms of a single unit hand-held WAVE recorder, the current contenders are the Edirol R-09 and the BossMicro. The files produced by these units can be transferred to your computer using USB.

3. It is possible to add a WAVE recorder unit from Belkin to the new video iPod. If you already have a fifth-generation iPod, this only costs $59 and is definitely worth a try.

Microphone: For the units mentioned in #2 and #3 above, the built-in microphones provide decent quality recording and no additional microphones are needed. Because these units are small and have no moving parts that can make noise, they can be used as if they were microphones. For most laptop computers, you need to use an additional external microphone. The choice of a good microphone depends on the nature of your recording environment and your recording unit. A good algorithm to follow is that you should never use a microphone that costs less than $100. By default, these units record at CD quality which is stereo and sampled at 44,100HZ. If you are going to analyze by ear, the stereo (cocktail party) effect is worth approximately 30 dB of signal-to-noise ratio. In some cases, you may wish to use external microphones so that you can put one mike close to the child and one farther away, with their inputs set to about the same recording level. That way, when the child vocalizes softly, the close one gets a good signal for later analysis, yet when he or she yells, overloading the close one, the far one gets a good signal.

Decreasing Noise: Try to avoid recording near traffic or other external noises. Rooms with carpets have fewer echoes and floor noises than rooms with hard floors. Ongoing noise from televisions, radios, stereos, washing machines, computer fans, and other appliances can ruin a recording. If noise is coming through an open window, consider closing it. Try to minimize spurious background noises or noises caused from bumping the microphone onto hard surfaces or jostling the microphone cord. Try to keep the microphone out of clear view so that the child will not try to talk directly into it.

Some researchers prefer to do their work in sound-proof rooms in a laboratory. Although it may be difficult for infants and mothers to adapt to the needs of getting to a laboratory, the results can be better acoustically. Although children produce less vocalization in such an environment, the nature of their vocalizations is similar, as has been demonstrated in Ledeweg et al. (1994).

You can also use the tape recorder as a notebook. You can record commentary directly onto the tape when the child is not talking and you are in a different room. You can begin each casette with a statement of the date, the year, the name of the child, the nature of the setting, and so on. This practice is very helpful in identifying tapes that have been otherwise mislabeled.

If you wish to record mobile groups of children, you will need to associate a particular microphone and a particular recording channel with each child separately. If you have only two children, you can use a single stereo recorder. If you want to study more children, you will need separate recorders. You will then have the problem of trying to time-lock the multiple tape sources when you come to transcription. When children are mobile, it is often difficult to follow each child about with a tape recorder. A solution to this problem is to use a transmitting microphone with a receiver connected to a stationary tape recorder.

In some social situations, speakers will become self-conscious when they know they are being recorded. This even occurs with children. One solution to this problem is to record without the knowledge of the people being recorded. However, this solution may run afoul of Human Subject institutional review board rules. If you record in a clandestine manner, it is imperative that you explain this later to your informants and explicitly request their permission to use the recording. If they do not give you this permission, you will need to erase the recording. Much of the British National Corpus was recorded in this way (Crowdy, 1993), but somehow it has not been erased.