Abstract: The Speech Transmission Index (STI) is an objective measure that predicts speech intelligibility. Test signals are played back through a channel under test. An STI analyzer at the channel output calculates an index between 0 and 1, indicating intelligibility. Over the years, various test signals have been used for measuring the STI, all based on the same principles but differing in the modulation frequencies tested and octave bands covered by the signal. The invention disclosed is a new method for constructing test signals: not just the transfer of modulations on a carrier signal is analyzed, but also the carrier signal itself This apprach leads to more accurate STI measurements that correspond more closely to the ideal (theoretical) STI and to subjective speech intelligibility. Shorter measuring times are achieved without compromising the accuracy of the measurement, while extending the range of systems to which the STI can be reliable applied.

Abstract: A system and method is described for monitoring the recording quality of a microphone. Some microphones, mostly in fixed installations, already feature a (piezo) sounder built into the microphone housing which is used to assess whether the microphone is functioning properly. At random or fixed intervals, the sounder produces a known signal; the microphone signal is then measured to determine if the microphone is working The disclosed invention comes down to extension of this principle by not only testing if the signal is reproduced at the correct level, but also using the sounder to measure the transmission quality of the microphone. The sounder produces a signal designed for this purpose. Upon playback of this test signal, the microphone signal is analysed to determine the overall transmission quality of the microphone, and evaluate the influence of factors that degrade quality, such as noise, bandwidth limiting, dynamic range and reverberation.

Abstract: The Speech Transmission Index (STI) uses the modulation transfer function to characterize speech communication channels with a single index. This index accurately predicts speech intelligibility. In order to measure the STI, a device or software is needed that utilizes an artificial test signal to estimate the modulation transfer function, and to derive the STI from that function. In practice, many STI measurements are found to be invalid and inaccurate, for two reasons: (1) the measurements are carried out in test conditions for which by design the STI is not intended; (2) equipment is used that does not meet specifications and requirements. A procedure is described to automatically verify if conditions for obtaining valid STI results are met. If possible, corrections are applied to compensate for incorrect settings and poorly adjusted measuring equipment. If automatic correction of the problem is not possible, then a warning is generated.

Abstract: A system and method is described for automatically limiting the sound exposure incurred by users of sound reproducing devices, by continuously tracking and evaluating the cumulative sound exposure dose. Instead of limiting the average sound level to a fixed maximum, the user retains freedom to adjust the sound volume to higher or lower levels. However, if the system determines that the overall cumulative sound dose is approaching a certain pre-set value presumed to be potentially hazardous, the gain and compression settings of the sound reproducing device are modified in order to limit sound exposure. This is done in such a way that the interference with the user experience is minimized. Optionally, the user is also provided with controls to temporarily boost the sound level, which then gradually falls back to a level that is acceptable for prolonged exposure. The sound limiting system starts acting more quickly and aggressively as the tracked sound exposure dose becomes higher.

Abstract: System for giving intelligibility feedback to a speaker (1), speaking for an audience (2), comprising a first microphone (3) at the speaker's side and a second microphone (4) at the audience's side. Both microphones are connected to processing means (5) which are arranged to compute an intelligibility value based on both microphones' signals. Signalling means (6), preferably at the side of the audience, are arranged to generate an intelligibility feedback signal depending on the calculated intelligibility value. The signalling means being arranged to generate said intelligibility feedback signal in an optical form, visible for the speaker concerned. Wireless connection means (19) may interconnect the microphones, the processing means and the signalling means.