To make a comparison between various microphones, this term was introduced to indicate the power output of a nondirectional mike in relation to a directional mike of equal sensitivity in a diffuse sound field. An ideal cardioid mike has a DC of 3. Since the intensity of sound decreases as the square of the distance, the cardioid mike may be used at a distance of 1.7 times farther than a nondirectional mike with the same amount of disturbing ambient noise.
"My Wife’s sister had many old 33 LPs that had seen better days. On one of her visits to our house she asked if I could try and record some of her albums to cassette tapes as the LPs were really becoming worn and scratched. I recorded a few of the old albums, but gave up because the quality of the tapes was not any better than the LPs. My ..."