Archive for March, 2011

How to Properly Make Concealed Audio Recordings

Tuesday, March 1st, 2011

concealed audio recordingAn Ounce of Prevention: Tips on Better-Quality Audio Recordings

The most common form of concealed audio recording is made using a pocket digital recorder. Some micro cassette recorders are still in use today and work very similarly to digital pocket recorders, except microcassette recorders use recording tape and digital recorders store the audio on a microchip.

While all of the recording techniques apply to essentially any form of concealed audio recorder, for purposes of this article we focus on digital pocket recorders.

First, and very important, do not record with the voice activation-setting turned on. While this setting may let you record longer, voice activation settings can clip words on the recording which may result in a lower-quality evidence recording. Content that is lost or clipped may make or break your purpose for making the recording in the first place.

Next, it cannot be emphasized enough: Always use new and quality batteries for all recordings. Hours and money can be spent attempting to fix recording-speed problems due to weak batteries. The price of new or proper-size batteries is far less costly than the hours of lab/studio time spent to correct a speed problem due to weak batteries. On the same subject, it’s wise to have a ready, second set of fresh batteries as a backup for recording.

During actual recording, be as close as possible to the sound source. The more distance between you and your sound source (person talking), the lower the available volume (acoustic energy) you will have to capture on the conversation clearly on tape. This is probably the #1 technical mistake I encounter with concealed recordings.

Avoid extraneous noises. Take note of nearby appliances such as furnaces, refrigerators, air conditioners, TVs, radios, etc. which create unwanted background/humming noises and detract from recording clarity. Be mindful of recording too close to moving vehicles and, obviously, airplanes or loud exterior sounds can surely interfere with clear recordings. While some sources may be unavoidable, any noises competing with your sound source have the potential to ruin clarity of the conversation.

For example, I once had a woman provide me with a tape where her ex-husband was speaking right next to the TV.  Avoid extraneous noises. Take note of nearby appliances such as furnaces, refrigerators, air conditioners, TVs, radios, etc which create

Regarding recording speed, most digital pocket recorders have one speed setting. Micro recorders have more than one speed, usually two speeds. The first speed (slow) is 12; normal speed is 24 (faster); some makes and models vary. You may want to pre-record a test for yourself first – to be confident about the recording speed or sample rate (if digital) you choose and be familiar with the recording function and playback buttons, etc of the unit you use. If you are recording a long meeting/ conversation, it’s O.K. to record on the slow speed if using a micro-cassette or low sample rate if using a digital recorder. That way you will have plenty of room for your entire conversation.

TIP: If you have a micro cassette tape length of 60 minutes, remember that there’s only 30 minutes per side; flipping the tape over is what gives you the full 60 minutes. This time is doubled to 60 minutes per side when a recording is made at the slow speed.

Where to conceal the recorder is very important. For men, it’s best to put the micro cassette in a pants pocket with the microphone facing the sound source, away from your body. Top-cut-pocket pants (like jeans) work better than side-cut-pocket pants (like dress slacks). That way, the built-in microphone can be more easily exposed without it falling down into the pocket, becoming covered by material.

Sport coats are also good for camouflage drapery as long as they don’t block the sound too much. Remember, you don’t want your subject to know you are making the recording. Inside sport coat pockets is generally O.K., but I recommend a test recording to determine quality before the desired recording is made. Sport coats with thick fabric, like wool, insulate sound, making the volume level lower than desired. Similarly, silk or other materials that rustle too easily with even slight movement will create unnecessary noise and possible sound quality problems.

An external microphone is the best way to capture reliable sound quality. However, not all digital and micro cassette recorders have external microphone inputs. For $30-$50, you can purchase a lavaliere microphone at Radio Shack or on Amazon for very reliable sound quality. An external microphone can be concealed elsewhere while the recorder rests in a pocket.

When recording audio evidence, remember to sit as still as possible. Having fabric rub against the microphone (external or built in) creates a rustling sound that is very difficult to remove. When putting the digital or micro cassette recorder in your pocket, try to create a gap between the built-in microphone and the fabric of your clothes.

Regardless, of what equipment is used, it’s prudent to conduct a test recording prior to the actual recording, and make recording volume and make clothing adjustments as necessary.

Ladies definitely have the advantage by carrying a purse to conceal the recorder. When placing the micro cassette into a purse, be sure the microphone is as exposed as possible and facing the sound source. Try not to move the purse around too much to avoid rustling or scratching sounds that can hamper the recording.

Put the recorder into record; position just BEFORE arriving at the location where the recording is to be made. It doesn’t matter if you have some sounds recorded of you walking into the location and this helps ensure that your concealed recorder remains undetected.

Final reminder: Make a test prior to recording to be sure the recorder is functioning properly and recorded sounds are as clear as possible. Listen to the playback of your test and make sure you are pleased with the results. If not, make adjustments until you are.

I hope this information assists you in helping clients save money and avoid sound-quality errors when making a concealed audio recording. Remember, an ounce of prevention is worth a pound of cure.


 photo credit: Zoom H1 Handy Recorder via photopin (license)