In This Section
Journal of the AES
2009 May - Volume 57 Number 5
Objective Speech Intelligibility Measurement on the Basis of Natural Speech in Combination with Perceptual Modeling
Because the subjective evaluation of speech intelligibility in degraded communications systems is very time consuming, an objective measure would be a valuable tool. This paper shows that a simple extension of ITU-T Recommendation P.862 achieves at least a 0.8 correlation between subjective and objective intelligibility scores. Additional enhancements raised the correlation to around 0.9. Tests used CVC words embedded in a carrier sentence in the subjective test and a concatenated CVC string in the objective PESQ measurements.
An endfire loudspeaker array that radiates sound in the direction of the axis on which the loudspeakers are placed offers an alternative configuration for creating narrow spatial beamwidths. The basic theory of such arrays was investigated in a parametric study that explored the influence of the number of loudspeakers, their spacing, the length of the array, and the stability of the signal processing algorithm to create optimal beams. A prototype system was tested by simulation and measurement to confirm the parametric analysis. When the directional patterns of the individual loudspeakers were taken into account, the resulting directionality index improved by 3 dB.
Participant Testing of AM Broadcast Transmission Bandwidth and Audio Performance Measurements of Broadcast AM Receivers
In trying to raise the quality and popularity of AM broadcasting, a study explored listeners' attitudes toward transmission and receiver bandwidths. Results suggest that for highly compressed audio, such as rock or pop music, listeners heard very little difference between 7 and 10 kHz. However, for audio with fewer masking characteristics, such as speech and classical music, listeners preferred lower bandwidths of 5 to 7 kHz because they reduced real-world noise from adjacent channels. More is less; 7 kHz may be optimum for AM broadcasting.
Understanding heat production in moving-coil loudspeakers has allowed for using designs and materials that prevent the physical damage due to high temperatures. However, when high power bursts increase voice-coil temperature, the loudspeaker experiences power compression, reducing the effective sensitivity and changing the frequency response and damping. Working with music signals, after a sudden increase in applied power, the sound level fades as temperature rises, possibly affecting the listener's experience.
Standards and Information Documents
AES Standards Committee News
There is a growing awareness of the problems of intelligibility that arise for people with hearing impairments when they listen to reproduced sound. Difficulty understanding the content of spoken material in particular can affect both live performance situations involving PA systems and domestic listening situations. It naturally affects the elderly more than the rest of the population, because the incidence of hearing impairment is greater in this sector, but it is by no means irrelevant to many other groups that may suffer hearing difficulties of one kind or another. In this article a number of recent AES convention papers relating to hearing enhancement are summarized.