Recent Progress in Acoustics

V. O. Knudsen

Some recent developments in acoustics, especially in Germany, Russia, and in the author's laboratory, are reviewed. Experiments by E. Meyer, of Berlin, help to clarify the differences between geometrical and diffuse reflections of sound in rooms, and reveal the nature of some of the errors inherent in reverberation measurements. Meyer also describes special absorbent materials, as thin wood panelling or stretched oilcloth, which are selectively absorbent for low frequencies. S. Rschevkin, of Moscow, describes a method for prolonging, diminishing, or otherwise modifying the reverberation in a room by means of Helmholtz resonators. — A new electroäcoustical device for the artificial production of vowels, by K. W. Wagner, of Berlin, is capable of generating typical German vowels that can not be distinguished from the originals. The oscillogram and sound spectrum of the artificial vowel resemble more closely the oscillogram and sound spectrum of the original vowel than do two sets of oscillograms and sound spectra of the same vowel “picked up” at two different microphone positions in the same room. The experiments reveal the nature of sound distortion caused by reflections from the boundaries of a room, and show that the ear tolerates considerable distortion. — The paper concludes with a review of some recent work undertaken by the writer, including resonance in rooms, the acoustical design of broadcasting studios, and vistas in musical acoustics.

Print ISSN
Published
1937-09
Content type
Original Research
DOI
10.5594/J17370