Difference between revisions of "Audio filtering of the Trayvon Martin 911 call" - Rhea

Revision as of 22:56, 20 April 2017

Audio Filtering of the Trayvon Martin Shooting 911 Call

by Marlow Rumreich

Background

On February 26, 2012, neighborhood watch coordinator, George Zimmerman, shot Florida teen Trayvon Martin. There are many conflicting accounts about the circumstances that led up to the shooting, including possible injuries of Zimmerman by Martin. Key evidence in this case was an audio recording of a 911 call made by a neighbor that captured screams and gunshots from the incident. Because of the relatively poor quality of the recording and the ambiguity of the screams, there was intense debate during trial as to which party (Zimmerman or Martin) was the source of the screams. Both the defendant and the persecution had experts attempt to improve the quality of the audio in the call in order to demonstrate that their client was the source of the screams.

The goal of this exercise is to improve the quality of the screams in the background of the call in order to obtain a better-informed view of the events that transpired right before Martin was shot. The quality of the audio will be improved through simple noise filtering in MATLAB, as shown in the following sections.

Filtering of the Signal

Source for original audio: https://www.youtube.com/watch?v=AYxJieDtLo0

Conclusions

Although it is not possible to provide a definitive answer about whether the screams came from Martin or Zimmerman, this improved signal may be able to help listeners better come to their own conclusions. I have included links to samples of both Trayvon Martin's and George Zimmerman's voices for comparison.

Zimmerman Voice (911 call): https://www.youtube.com/watch?v=L04Vh4do6bY

Trayvon voice: https://www.youtube.com/watch?v=jylS4MXCqXY

Sources

http://www.washingtonpost.com/wp-srv/special/nation/last-minutes-trayvon-martin-911-calls/