The lungs and the muscles used in breathing provide the source of power for speech sounds, and thereby control to a considerable extent the loudness of the emitted sound.

The amount of power used in speech is surprisingly small, however. The vowels, which are the most powerful speech sounds. average about 100 microwatts, with peak values of about 2000 microwatts. The voices of persons capable of very loud speech may reach peak-power values of 5000 microwatts. On the other hand. the minimum in speech power is probably about 0.01 microwatt. and occurs when the sound /θ/ is pronounced.

Therefore, a telephone system must be capable of handling a range of speech intensity of 500.000 to 1, or 57 dB. For ordinary conversation. the range is considerably less, being approximately 10,000 to 1 or 40 dB.

The power used in the production of music is much greater than that used for speech, varying from about 4 microwatts for a softly played violin to nearly 70 watts for a full symphony orchestra. Thus the intensity range for music is about 20,000.000 to 1 or 73 dB.

Based on studies of a number of individuals, the average power used in American speech is 10 microwatts; therefore, if a million people were engaged in conversation simultaneously. their combined average speech power would be approximately equivalent to that consumed by a 10-watt electric light bulb.

In the August, 1951, issue of IRE, Mr. Ted Powell explains communication between moths. The female moth radiates infrared energy at a wavelength of about 8 microns. Radiation is indicated by the fact that the temperature of a female moth is about 11 degrees above that of her surroundings. The male moth has an antenna system consisting of a series of hairs ranging from 40 to 80 microns in length, in 4-micron steps. These steps are the familiar half-wave intervals so common to HF arrays.

Labels: Grand Blueprint

¶ 3:57 PM