A high-quality digital radio-frequency capacitor microphone with improved dynamic range.

Capacitor microphones are widely used to transduce sound waves into electrical voltages. The converting capacitor can either be operated in baseband (audio-frequency) or passband (radio-frequency, RF). A baseband operation can use a straightforward circuit implementation while a passband operation becomes more complex. The advantage of operating the capacitor in passband is a drastically lowered sensor impedance leading to superior performance, especially at high humidity levels. In this work, a digitized RF microphone is presented. Measurements prove the microphone to exceed commercial state-of-the-art small-diaphragm capacitor microphones in signal-to-noise ratio. Additionally, as the signal is digitized before demodulation, the electrical low-frequency 1/f-noise is circumvented. Furthermore, an all-digital gain ranging approach is presented, which is especially suited for the proposed system. The approach increases the system's dynamic range by digitally adjusting and correcting the microphone's sensitivity.

Changes in room acoustics elicit a Mismatch Negativity in the absence of overall interaural intensity differences.

Changes in room acoustics provide important clues about the environment of sound source-perceiver systems, for example, by indicating changes in the reflecting characteristics of surrounding objects. To study the detection of auditory irregularities brought about by a change in room acoustics, a passive oddball protocol with participants watching a movie was applied in this study. Acoustic stimuli were presented via headphones. Standards and deviants were created by modelling rooms of different sizes, keeping the values of the basic acoustic dimensions (e.g., frequency, duration, sound pressure, and sound source location) as constant as possible. In the first experiment, each standard and deviant stimulus consisted of sequences of three short sounds derived from sinusoidal tones, resulting in three onsets during each stimulus. Deviant stimuli elicited a Mismatch Negativity (MMN) as well as two additional negative deflections corresponding to the three onset peaks. In the second experiment, only one sound was used; the stimuli were otherwise identical to the ones used in the first experiment. Again, an MMN was observed, followed by an additional negative deflection. These results provide further support for the hypothesis of automatic detection of unattended changes in room acoustics, extending previous work by demonstrating the elicitation of an MMN by changes in room acoustics.