Speaker Input Research Articles

Adaptive array noise suppression of handsfree speaker input in cars

Handsfree speaker input of mobile telephones is most desirable today in order to enable safe operation in cars. This is also a prerequisite for voice control of car devices. This paper presents an "on the road" evaluation of the performance of an adaptive microphone array for speech enhancement in cars. The results show a signal-to-noise ratio (SNR) improvement in the range of 10-15 dB over the telephone frequency range with a slight favour for higher frequencies when driving at normal speeds.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Linguistic and Conversational Adjustments to Non-Native Speakers

At least 40 studies have been conducted of the linguistic and conversational adjustments made by native speakers of a language using it for communication with non-native speakers. The modifications sometimes result in ungrammatical speech. Generally, however, they serve to provide input that is well-formed, a sort of linguistic and conversational cocoon for the neophyte second language acquirer. Most of the findings hold across age groups, social classes and settings, although some differences, both qualitative and quantitative, have been noted in these areas, too.In making the adjustments described, native speakers appear to be reacting not to one, but to a combination of factors. These include the linguistic characteristics and comprehen-sibility of the non-native's interlanguage, but particularly his or her apparent comprehension of what the native speaker is saying. The adjustments appear to be necessary for second language acquisition, in that beginners seem unable to acquire from unmodified native speaker input. There is some doubt as to their sufficiency in this regard.

The audibility of Doppler distortion in loudspeakers

The existence of Doppler distortion in loudspeakers was demonstrated more than 30 years ago, but the question of whether or not such distortion is of significance in music reproduction has not been settled. In this study the audibility of Doppler distortion in simple direct radiators is investigated both theoretically and experimentally through (1) an analogy to tape-machine flutter, (2) an analysis of the effect of normal listening-room conditions on Doppler distortion (for a given low-frequency power the radiation-load and reverberant-field correction factors typically reduce this distortion to 0.36 of its value on the axis of a speaker radiating into anechoic half-space), and (3) double-blind listening tests. An eight-member jury compared music reproduced in two modes, one of which was essentially free of Doppler distortion. In one experiment, two recordings were made of the output of a speaker, one with a sharp bass-attenuation filter in the speaker input circuit and the other with the same filter moved to the microphone circuit. In a second experiment, on-axis and off-axis speaker output were recorded in an anechoic chamber, the speaker input circuits being compensated to make the frequency responses in the two modes equal. The theoretical analysis indicates that for any practical cone velocity Doppler distortion will be less audible by an order of magnitude than the flutter of a 15-ips tape machine that meets the NAB Standard. The experimental results provided confirming evidence that it is inaudible.

A Sound Source for Investigating Microphone Distortion

Theoretical and experimental data are presented on a standing wave resonance system for obtaining a high pressure sound field with a prescribed harmonic eliminated. It consists of an eight‐foot iron pipe ten inches in diameter, and a five‐sixteenths‐inch wall, with an eight‐inch dynamic speaker at one end and a movable iron piston at the other. A pressure of 1000 dynes per cm2 at 100 cycles per second is readily obtained with a speaker input of less than 0.5 watt. Harmonic attenuation factors of 68 to 1 and higher are obtained. Hence the sound field is free of a given harmonic to within a few hundredths of one percent with three percent harmonic in the speaker input voltage.

A Sound Source for Investigating Microphone Distortion

Theoretical and experimental data are presented on a standing wave resonance system for obtaining a high pressure sound field with a prescribed harmonic eliminated. It consists of an eight-foot iron pipe ten inches in diameter, and a five-sixteenths-inch wall, with an eight-inch dynamic speaker at one end and a movable iron piston at the other. A pressure of 1000 dynes per cm2 at 100 cycles per second is readily obtained with a speaker input of less than 0.5 watt. Harmonic attenuation factors of 68 to 1 and higher are obtained. Hence the sound field is free of a given harmonic to within a few hundredths of one percent with three percent harmonic in the speaker input voltage.