SRT in filtered noise plateaus asymptotically beyond a threshold attenuation

Evidence

Speech Reception Thresholds (SRTs, SNR yielding 50 % intelligibility) were measured in the presence of a speech target and a speech-shaped noise. Target or noise was attenuated above or below 1400 Hz at different levels of attenuation in order to vary the SNR in the low or high frequency regions. The SRT is expected to increase along with the attenuation level in the case of a filtered target. Conversely, when the noise is filtered, the SRT should decrease while the attenuation level is increased. In both cases, SRTs are expected to remain unchanged and form an asymptote beyond a certain attenuation level: variations of SNR should not influence speech intelligibility any longer. — Dijk, Pim van, Physiology, Psychoacoustics and…, 3539