While Dolby A operates across the whole spectrum, the other systems specifically emphasize the audible frequency range where background tape hiss, an artifact of the recording process that is similar to white noise, is most noticeable ( usually above 1 kHz, or two octaves above Middle C ).
42.
The amount of information you will be able to collect will obviously depend on the sampling rate, and, depending on your reason for collecting the data, its usefulness may be limited by the audible frequency range of human hearing .-- talk 20 : 46, 13 October 2011 ( UTC)
43.
You might say the subwoofer's range extends from bass to deep bass; of the audible frequency spectrum of 20 to 20, 000 Hertz ( cycles per second ), a subwoofer typically covers the segment below 100 Hz, but its real value lies in the narrow, difficult zone from 40 to 20 Hz.
44.
The idea is to reduce the incoming frequency, which may be, say 1, 500, 000 cycles ( 200 meters ), to some suitable super-audible frequency that can be amplified efficiently, then passing this current through a radio frequency amplifier and finally rectifying and carrying on to one or two stages of audio frequency amplification.
45.
:Modern SONAR is far outside of the range of frequencies that humans can hear-but since many submarine movies are set in World War II, we're not really talking about modern SONAR . I think the technology of the time would have made using audible frequencies quite attractive since you wouldn't need any fancy electronics to decode it-just a guy with sharp hearing.
