Forensics Questions and Answers

Q: Can you make very soft voices audible?
A: Yes, if there is enough signal to work with. Gat3 has successfully recovered a mostly inaudible whisper from a law enforcement wire recorded poorly to micro cassette.

Q: Do you alter the original recording in any manner?
A: No. The original is played back on an appropriate device for transfer to the digital domain.

Q: Can you recover anything from an erased tape?
A: In most cases, it is doubtful whether meaningful information can be recovered from an erased tape. The erase head of a recorder precedes the record head and is automatically activated when record mode circuits are engaged. When recording, the erase head places an alignment tone on the tape just prior to the record head recording. This alignment is that of the magnetic particles of the tape, which is done by placing a high frequency of between 50 khz and 100 khz on the tape to ensure proper patterns conducive to recording, thus "erasing" previous material. However, what it does not do is penetrate deeply (saturate) into the physical tape and sometimes it is possible to recover some low frequency signal. This signal may or may not be intelligible. That will depend on the amplitude and quality of the original signal, and the quality of the physical tape. Also, head alignment differences between players may yield some results, and it is always possible the erase head of the original recording equipment has malfunctioned and some previous signal remains. However, the chance of recovering anything useful is exceedingly small.

Q: My tape is damaged. Can you repair it?
A: It depends on the nature and severity of the damage, as well as whether it was damaged during playback or recording. Gat3 has been very successful salvaging damaged tapes.

Q: I have a message on a digital voice messaging system that needs forensic examination. What do I do?
A: Gat3 can retrieve the message directly from the voice messaging system and a digital recorder.

NOTE: Do not attempt to record this yourself by holding a microphone to the telephone earpiece. This usually results in a very unsatisfactory recording with the voice being very faint or garbled, as well as the possibility of there being interfering background noise. Also, unless you are very familiar with digital recording requirements, do not record this to your computer. This often results in an incorrect bit depth and sample rate, with the audio being digitally distorted. If this happens is usually nothing that can be done to correct it.

Q: My recording sounds like chipmunks. Can you fix it?
A: Yes.

Q: Do you have to work from an original recording, or is a copy suitable?
A: It is always preferable to work from the original recording. It is doubtful whether a copy will be given the credibility you might like if it is to be used as evidence in a court of law. Also, a copy has a loss of fidelity, and thus detail. The original should be used for analysis and processing whenever possible.

Q: Do you return the completed project on cassette or CD?
A: Completed audio projects can be returned on standard analog cassette, digital tape or CD. We prefer CD as it creates very little additional noise floor.

Q: Do you work only for attorneys and law enforcement?
A: No, anyone can obtain Gat3’s services.

Q: Can you eliminate annoying background noise such as a TV, dishes clattering, or traffic noise?
A: These sounds are called masking signals and selective elimination depends on how much of the masking signal is mixed at the same frequency as the desired signal. Masking signals can always be reduced, but the possibility of total elimination depends on many factors. A masking signal can be as much as four times the amplitude of the desired signal before desired dialogue/signal information is completely lost. Note that low frequencies can completely mask higher frequencies, but rarely will higher frequencies completely mask those lower. In the latter case, the problem is more one of distraction than of complete obliteration.

Q: Can you eliminate hum?
A: Yes.

Q: Can you tell if a tape has been altered?
A: In most cases, it is possible to detect whether a tape has been altered. Sudden changes in background ambiance, frequency spectrum and amplitude are common signs that an alteration has occurred. There are other techniques which can also be used to detect alterations to an original recording.

Q: Will you supply a report?
A: Yes, if requested. The report may be a brief procedural overview, or an extensive detailed report with high quality graphics for court presentation. Report writing is billed at the standard Gat3 forensic hourly rate.

Q: Can you estimate cost?
A: Gat3 bills by the hour, with a minimum charge of $125. The real difficulty of estimating cost for a particular job is estimating the amount of time required to perform the tasks involved. For most forensic audio jobs, the time required is a function of the length of the recording, the quality of the recording, the nature of the task(s) to be performed, and the urgency with which results are required.

Gat3 is committed to helping clients find cost-effective solutions to their problems, and may be able to help minimize the cost of a particular job by working with the client to determine precisely what is needed. For example, it may be the case that on a given tape, intelligibility is only an issue for a few words or phrases. In such cases, Gat3 will help the client determine which of those words and phrases need intelligibility enhancement, and will focus only on those areas of the tape. This can result in significant savings.

Naturally, the more information Gat3 has about the nature of the job, the better we can estimate the cost. A description of the problem, for example, in a telephone call provides only the broadest parameters and rarely provides sufficient information for a reliable estimate of the time required to perform the task. Even after listening to the tape, it is difficult to make a reliable cost estimate because of the extreme complexity of the procedures involved in forensic audio.

Q: Will you evaluate my recording before I decide to continue with the work?
A: Yes, but there is a service charge for this service. You must pay the minimum retainer of $75. If you decide to continue, the retainer is applied toward the total charge. Call for details.

Q: Will you make a transcript?
A: Yes. It is advised that you allow us to handle the transcription, especially when court testimony or an affidavit may be necessary. In addition, Gat3 will allow anyone you designate to come into the studio and make a transcript. Gat3's playback facility is far beyond the quality found in most offices or homes, thus this is a very good way to obtain an accurate dialogue decoding and transcription. Digital playback of an enhanced recording has more detail (clarity) than an analog copy. Also, special decoding playback techniques can be used such as momentary time expansion, section looping, or setting the eq of a section to the specific hearing ability of the decoder.

Q: How do I pay you?
A: A retainer is required for all forensic work. The amount will vary, depending on the type of investigation and the amount of time it is expected to tie up Gat3 resources. The minimum retainer is $75 and may increase to several thousand. Completed work is returned via FedEx. Credit cards are accepted. International clients must prepay before shipping.