Frequency

Matter waves have a broad range of frequency, from zero up to the current practical upper limit of about 1,000,000 cycles per sec (cps) in use in some ultrasonic-therapy and submarine-detection studies (Figure 3-1 (c)). The human ear is most sensitive from ~50 to ~10,000 cps; the range of man's ear, however, may be from 20 to 21,000 cps. This, then, is the auditory or sound range. Speech requires 60 to 500 cps. The piano ranges from 27.2 to 4138.4 cps. The great basso profondo, Italo Tajo, could reach a minimum of ~60 cps; the diminutive coloratura soprano, Lili Pons, could hit 1300 cps on a good day. Of course, these are the basic frequencies, and it is understood that a basic frequency generated by any physical vibrator will contain overtones, or harmonics, which are multiples (2x, 4x, even 8x) of the basic frequency. The quality of the tone is determined by the sum of all the components: the basic frequency plus its harmonics.

Training and youth combine to produce a receiver which can hear low power sound up to 12,000 cps. Some musicians can detect overtones from their instruments up to 14,000 cps, but these are few. Most of us can detect frequencies up to 18,000 from a signal generator, if the signal is intense enough, and the odd person can detect up to 21,000 cps. Dogs do it with ease. Porpoises have a phenomenal sonic system in their heads which can sweep frequencies repetitively from a few cycles to many thousands of cycles —both send and receive.

Below and overlapping the auditory range for man is the range (0 to 50 cps) of blast and shock waves, earth tremors, water waves, and the like. The masseur will use vibrations 1 to 50 cps; a ship will roll at 0.1 cps. An air hammer operates at ~ 15 cps, and we hear the overtones.

Above the range of sound, from 20,000 up to > 1,000,000, lies the important range of ultrasound, and the science and technology known as ultrasonics.