Tech Tip Thursday from Facebook

MP3 compression is great for making the recording times of a digital recorder longer. However, MP3 is a "lossy" compression algorithm. As the bit rate is decreased, the amount of "important" data that is lost increases. If you must use MP3 compression when recording, always set the highest bit rate that gives you the duration you need.

Bit rate affects the size of the resulting MP3 file. Lower bit rates produce smaller files (superior compression). However, lower rates also equate to more loss. Some loss is nearly unnoticeable. However, as bit rate is sacrificed for smaller file sizes, the loss becomes audible.

Loss in audio files can manifest itself in several ways. Sounds become distorted and harder to distinguish. Harshness and ringing are terms often used to describe these effects. In the world of paranormal investigation, it is vital to be able to identify sounds and debunk those that are man made. This becomes less possible as quality decreases (as bit rates are lower) and may lead to false positives or mistaken EVPs.

So what is a good bit rate? It really depends on the quality of the other components in the signal chain as well as the ear of the listener. As a general rule of thumb, MP3 bit rates should be set to 128kbps or higher. However, if you have high quality recording components and good ears, rates of 256kbps or higher are recommended.

Also note -- these rates refer to the MP3 compression algorithm. Other audio compression technologies (such as WMA or OGG) are different algorithms and can produce acceptable audio with lower bit rates.

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