Aside from video evidence, there is nothing more powerful in court than a clean, crisp audio recording. Achieving a useful audio enhancement is one of the goals NCAVF strives to accomplish in the studio every day. Whether we are attempting to identify a suspect’s voice or determine the details of action, our main goal is to make all recordings clear not only to our staff, but to the attorneys and to the jury involved in the case.
If attorneys or investigators could discern for themselves what was said in an audio clip, they wouldn’t be using our forensic services in the first place. That being said, more often than not, the recordings we receive are fairly inaudible. Incredibly static, disjointed and noisy recordings are a common challenge here at NCAVF.
There are different reasons for poor audio quality. For example, surveillance audio equipment is usually hidden, blocking microphones from direct access to the sounds they are trying to record. Or, on devices like police DARS, the most important audio evidence is often recorded during times of intense physical activity – when mics are banged, accidentally covered, or knocked to the ground. When people call a 911 operator they are in high-stress situations, maybe even in fear of their life, and not able to communicate as clearly as they would otherwise. When you factor in the multiple circumstances, it is understandable that in the most dangerous, hectic moments, audio integrity can be jeopardized.
However, what may initially seem like unusable audio evidence, can sometimes be cleaned to the extent of being helpful in court. How do we do this?
When you hear a series of sounds, it can be hard to differentiate between the various pitches and volume levels. You most likely hear audio but can’t tear apart one source stream of sound from another.
When we are asked to enhance audio footage, we expect — based on the fact that someone came to us for help — that the evidence will lack clarity. We attempt to minimize those frequencies and audio source streams that muddle audio comprehension, and we attempt to strengthen the portions of audio that are crucial as evidence.
Here are some examples of audio we’ve enhanced for court:
In a jail yard, an informant was wearing a wired microphone while a suspect allegedly confessed a crime he had committed in jail. However, the alleged confession took place directly next to an air conditioner, which loudly hummed into the informant’s mic. On top of the hum, the yard was loud with inmate conversations and activity. We were asked to bring down the AC hum and minimize the sounds from the yard.
In a similar circumstance, the wiring to an informant’s microphone malfunctioned, giving off a constant buzz during the entire recording. We were asked to remove the buzz to help investigators.
Another case involved a 911 emergency call. We were asked to clarify and identify the voice in the home and create a transcript of all words we deemed audible. Proving that one party had either imagined or purposefully lied, the attorney for the defense was able to eliminate the possibile damage caused by the other side’s fabricated accusations.
We aren’t always able to enhance audio to perfection. But we do have the tools and experience to improve the quality of an audio recording in most cases.