Measurement of loudness

Abstract

T !jHE ultimate significant subI jective destination of original or _1_ reproduced sound and noise is the human ear. Therefore, the varied responses of the auditory system are particularly important factors in the re production of sound. One of the re sponse functions of the human hearing mechanism is loudness. The purpose of this paper is to describe a loudness meter based upon the fundamental principles of the loudness response of the human hearing mechanism. When a sound or noise of any quality or structure impinges upon the human ear, the magnitude of the resultant sensation is termed the loudness. It is the intensive attribute of an auditory sensation in terms of which sounds may be ordered on a scale extending from soft to loud. Loudness depends pri marily upon sound pressure but it also depends upon frequency and waveform of the stimulus. The units on the scale of loudness should agree with common experience estimates about the magni tude of the sensation. The measurement of loudness is a significant part of the audio art because the loudness of a sound or noise plays an important role in the reproduction of sound. Loudness is functionally related to sound pressure level, frequency, and waveform. Turning this around, the sound pressure level as measured by a sound level meter does not indicate the loudness of a sound. However, a con version can be made in the readings of a sound level meter employing octave band pass filters to obtain the loudness. This is indeed a long and tedious pro cess, as the exposition in this paper will show. What is required is a loud-