SOUND FIELDS AROUND THE HEAD/HANDSET SYSTEM AND THEIR EXPLOITATION FOR PRESSURE GRADIENT NOISE CANCELLATION
MP HOLLIER · 2024
Speech communication over the telecommunications network must often be attempted in conditions of high background noise.This is a' particular problem when the telephone is used outside, for example payphones and mobile phones.Under these conditions even face-to-face conversations can become difficult.This paper describes a novel noise cancelling handset which will make telephony possible in high levels of background noise.The user at the noisy location will benefit from reduced noise in the "telephony ear via the sidetone path and the far end user from reduced background noise sent to line.2.0 NOISE CANCELLING PERFORMANCE. Oh|ectlve PerformanceThe metric for the noise performance of a telephony handset is given in the CClTT recommendations and known as Delsm (or ASM) [1].Delsm = Sensitivi to Noise (dBV/Pa) Sensitivity to Speech (dBV/Pa)The measurement oi Delsm is specified on an LFtGP (Loudness Rating Guard-Ring Position) artificial head which does not simulate the obstacle effect of a human head and torso.This effect is important and an equivalent Delsm measurement was developed with the MK Type 4128 HATS (Head And Torso Simulator).The results are in the form oi a frequency spectrum, a more negative result representing greater discrimination of speech over background noise.