Index of content:
Volume 48, Issue 5A, November 1970
48(1970); http://dx.doi.org/10.1121/1.1912240View Description Hide Description
In 1964 an electronic system (“assisted resonance”) to lengthen the reverberation time over a limited frequency range was installed experimentally in the Royal Festival Hall, London. Following the success of this experimental installation, the frequency range covered was extended (to 58–700 Hz) and the installation made permanent. This paper describes the installation and operation of the permanent system, and its objective and subjective effects. Typically, the reverberation time in the empty auditorium has been increased in the 125‐Hz octave band from 1.4 to 2.5 sec.
48(1970); http://dx.doi.org/10.1121/1.1912241View Description Hide Description
A probe‐tube adapter for use with a 1‐in. condensermicrophone has been developed. The greater sensitivity of the 1‐in. condensermicrophone provides a means for measuring the sound‐pressure lever of pure tones generated in the human ear canal by application to the cranium of bone‐conducted tones. The greater sensitivity is particularly useful in the frequency range below 300 Hz.
48(1970); http://dx.doi.org/10.1121/1.1912242View Description Hide Description
Improved poling techniques have led to improvement in the piezoelectric activity of bulk polymers. Results now achieved approach the activity of conventional piezoelectric materials such as quartz, and further improvement is anticipated. The measured value of the piezoelectric strain modulus d 31 of a length expander bar of polyvinylchloride was 0.6×10−12 m V−1 and the electromechanical coupling factor k 31 was 0.6%. The response of a sample as an underwater sound receiver was −112 dB re 1 V/μbar.