The Frequency—Sensitivity of Normal Ears

H. Fletcher and R. L. Wegel
Phys. Rev. 19, 553 – Published 1 June 1922
PDFExport Citation

Abstract

Minimum Audible Pressure Variation for Tones of 60 to 4,000 Cycles.—The rather discordant results obtained by other investigators are briefly reviewed and are summarized in Fig. 1. In the present research an attempt was made to get results with a definite dynamical significance. A special air-damped telephone receiver held tightly to the ear, was excited by an alternating current of variable frequency from a vacuum tube oscillator provided with special low pass filters to eliminate upper harmonics, and the current strength was changed logarithmically by means of a special attenuator until the threshold was reached. The observations were made in a special sound proof room whose construction is described. The probable error is about 25 per cent. To reduce the results to absolute units, the system was calibrated in two ways, both involving the substitution of a condenser transmitter for the ear, the source of sound being a telephone receiver in one case and in the other a small thermal receiver inserted in the ear meatus or in a similar cavity in front of the condenser transmitter. Mechanical analogues of the vibrating systems involved in these measurements are described in an Appendix to help make the dynamics clear. While the unknown mechanical constants of the inner ear introduce some uncertainty, the agreement of the two calibrations indicates that the error is not large. Frequency-sensitivity curves were obtained for approximately 100 normal and 20 abnormal ears. So-called normal ears were found to vary widely in relative frequency sensitivity and in absolute sensitivity, and some audiograms show interesting individual peculiarities. But on the average, the minimum audible pressure variation increases regularly from about 0.15 dyne/cm.2 at 60 cycles to 0.001 dyne/cm.2 at 1,000 cycles and is then approximately constant up to at least 4,000 cycles.

Variation of Sensitivity with Deafness.—People who require throughout the speech range (600 to 4,000 cycles) about 0.1 dyne/cm.2 are called slightly deaf; those requiring 1 dyne/cm.2 can still follow ordinary conversation; those requiring 10 dynes/cm.2 need ear trumpets or other amplifying devices, and those requiring 1,000 dynes/cm.2 are totally deaf.

Attenuator for Varying the Current from an Oscillating Tube through Wide Ranges was constructed. It consists essentially of an artificial transmission line with resistance sections of series and shunt arms, so designed as to eliminate interfering effects between the various elements. The range of variation obtained is three million fold.

  • Received 1 November 1921

DOI:https://doi.org/10.1103/PhysRev.19.553

©1922 American Physical Society

Authors & Affiliations

H. Fletcher and R. L. Wegel

  • Research Laboratories of the American Telephone and Telegraph Company and the Western Electric Company, Inc.

References (Subscription Required)

Click to Expand
Issue

Vol. 19, Iss. 6 — June 1922

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review Journals Archive

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×