Analysis focus – Testing phonecalls in noisy environments
Whether they are walking down a noisy street or talking on speakerphone, telephone users expect clear voice transmission.
Sophisticated signal processing enhances human speech above background noise, but as there are different methods to test this capability, manufacturers cannot always be sure of the best one to use on their products.
Brüel & Kjær has investigated five different methods for the reproduction of background noise, including ETSI EG 202 396-1, Higher-order ambisonics, matrix inversion method, ETSI TS 103 224 and matrix inversion method optimized for a specific device.
For each method, the quality of the reproduced sound was evaluated both objectively and subjectively, at microphones close to a device under test and at the ears of a Head And Torso Simulator (HATS). A listening experiment evaluated the perceived quality of the sounds at points where telecommunication devices would typically be placed, around the head.
Following the experiment, Brüel & Kjær’s researchers found that the matrix inversion method – optimized for specific microphone positions, such as kdev/kbin – proved to perform the best, both in the objective and the subjective analysis.
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