Word: decibel
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...replace human hearing. A parabolic reflector picks up the sound from the mill, focuses it on a microphone. If the sound is at the most efficient level, the microphone current keeps a galvanometer balanced between two contacts. If it rises or falls as little as one-quarter of a decibel, the galvanometer makes contact on one side or the other, closing a circuit which starts or stops the flow of ore as the situation requires. More than 75 of these electric ears are already...
...clangorous world in which municipal antinoise campaigns have attracted wide and favorable attention, most laymen know that a decibel has something to do with the measurement of din, although few could define the term. Meanwhile acousticians have taken up a newer and less well-known unit, the phon, which may well become familiar to laymen because it is even more closely related to the sensibilities of the human ear than the decibel...
...decibel is an arbitrary unit such that, starting from the zero level or threshold of hearing, each increase of one decibel represents an increase of 25% in the physical intensity of the sound. The human ear has an enormous range. It is not pained by loudness until the sound is about ten trillion times as intense as a whisper at the threshold of hearing. Thus it is not very sensitive to small intensity changes. The decibel is intended to represent roughly the smallest intensity change which the ear can detect...
...unit of loudness. In the British journal Nature last week Dr. George William Clarkson Kaye of the National Physical Laboratory described the phon scale as "a loudness scale which is based on the accepted ability of the average individual to compare and match loudness." Thus, while the decibel is an objective measure of a sound's physical intensity, the phon is a subjective measure of its apparent loudness to the ear. There has been some difficulty with phons in international exchanges of research results because in the U. S. the decibel was generally used as a loudness unit...
...mouth of the amplifiers the intensity of sound will be about 140 decibels. A decibel is an arbitrary unit representing approximately the minimum intensity change which the human ear can detect. Every increase of one decibel multiplies the intensity by 1.25. One hundred and forty decibels is not 40% louder than 100 decibels, but 10,000 times louder. Loudest human shout ever recorded was 86 decibels. Other recorded loudnesses...