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Transaural synthesis using loudspeaker signals determined through contemporaneous ear canal calibration is proposed as an alternative to headphone presentation for critical psychoacoustical experiments. The proposed technique can afford greater accuracy, improved reproducibility, and continuous signal monitoring. It allows the experimenter to compare listener responses to real and virtual presentations. In this article, the advantages of transaural (three or four loudspeakers) compared to crosstalk cancellation (two loudspeakers) are shown through computer modeling and manikin measurements in a moderately reverberant room. Measurements employ binaurally challenging signals and speech from a distant source. Transaural synthesis is shown to be a better solution to the essential inverse problem resulting in reduced average synthesis amplitudes, fewer large-amplitude outliers, improved amplitude and phase accuracy for real and imagined sources, and improved noise immunity. Immunity to inadvertent listener head rotation depends sensitively on loudspeaker placement and is not an advantage in general. Appendixes review the relevant mathematical foundation and extend it to the relationship between ear canal signals and eardrum signals.

Transaural synthesis using loudspeakers is a powerful technique for conducting binaural hearing experiments while avoiding myriad problems caused by headphones. It is the most promising method to test binaural hearing for listeners using cochlear implants. Transaural synthesis is typically implemented using crosstalk cancellation, a technique whereby the left-channel signal and right-channel signal are adjusted so that reproduction by two synthesis loudspeakers results in near perfect transmission of the target left and right signals to the left and right ears (or processor microphones). Crosstalk cancellation has enabled precise experimental control over the stimulus delivered to each ear. Unfortunately, the 2×2 matrix inversion required for crosstalk cancellation can occasionally introduce spuriously large amplitudes for specific frequencies into the adjusted signals. These large amplitudes lead to perceptually salient tones. We demonstrate through simulation and experiment in a real room that adding a third loudspeaker and solving the resulting 2×3 problem using the Moore-Penrose pseudoinverse matrix yields dramatically fewer large amplitudes in the resulting adjusted waveforms. We have also conducted experiments to investigate the 2×3 system's robustness to inadvertent listener motions.Transaural synthesis using loudspeakers is a powerful technique for conducting binaural hearing experiments while avoiding myriad problems caused by headphones. It is the most promising method to test binaural hearing for listeners using cochlear implants. Transaural synthesis is typically implemented using crosstalk cancellation, a technique whereby the left-channel signal and right-channel signal are adjusted so that reproduction by two synthesis loudspeakers results in near perfect transmission of the target left and right signals to the left and right ears (or processor microphones). Crosstalk cancellation has enabled precise experimental control over the stimulus delivered to each ear. Unfortunately, the 2×2 matrix inversion required for crosstalk cancellation can occasionally introduce spuriously large amplitudes for specific frequencies into the adjusted signals. These large amplitudes lead to perceptually salient tones. We demonstrate through simulation and experiment in a real room that adding a ...

Lowpass noise with a sharp spectral cutoff generates a monaural noise edge pitch (MNEP) that listeners match with a sine tone having a frequency somewhat below the noise cutoff frequency (negative pitch shift). If the MNEP is a proper musical pitch, listeners should be able to identify musical intervals made using only the MNEP stimulus. Open-set MNEP experiments in the edge-frequency range of 600-2400 Hz found that four out of four listeners with musical training correctly identified octaves, fifths, fourths, and major thirds, proving that the MNEP is a musical pitch. The MNEP can be heard for edge frequencies at least as low as 100 Hz, but the negative pitch shift becomes larger than a semitone, consistent with a timing model of the MNEP having a fixed integration time. If the MNEP reflects the expected quasi-periodic timing response of the auditory system to a sharp spectral edge, the pitch should become inaudible if the edge frequency becomes too high for neural synchrony—expected to be about 5000 Hz....

When a conversation is recorded and then played back, listeners are aware of effects of the room that are not perceived in face-to-face conversation. The room effects, which are physically present, are said to be “squelched” under face-to-face conditions. Room effects include reverberation and coloration caused by reflections. The squelch effect has been attributed to the binaural nature of natural listening, based on binaural experiments with headphones [W. Koenig, J. Acoust. Soc. Am., {22}, 61–62 (1950)]. We report experiments on binaural and diotic listening to recordings of speech made at conversational distances in a room with normal frequency dependence of reverberation and a direct to reverberant power ratio between 1/2 and 1/3 at speech fundamental frequencies. Recordings were made with and without a head between the microphones. Listeners ranked the recordings in order of increasing perceived room effects. The data revealed a strong effect of distance, a weak effect of head diffraction, and an ad...