Noise abatement in office environments often focuses on the reduction of background speech intelligibility and noise level, as attainable with frequency-specific insulation. However, only limited empirical evidence exists regarding the effects of reducing speech intelligibility on cognitive performance and subjectively perceived disturbance. Three experiments tested the impact of low background speech (35 dB(A)) of both good and poor intelligibility, in comparison to silence and highly intelligible speech not lowered in level (55 dB(A)). The disturbance impact of the latter speech condition on verbal short-term memory (n=20) and mental arithmetic (n=24) was significantly reduced during soft and poorly intelligible speech, but not during soft and highly intelligible speech. No effect of background speech on verbal-logical reasoning performance (n=28) was found. Subjective disturbance ratings, however, were consistent over all three experiments with, for example, soft and poorly intelligible speech rated as the least disturbing speech condition but still disturbing in comparison to silence. It is concluded, therefore, that a combination of objective performance tests and subjective ratings is desirable for the comprehensive evaluation of acoustic office environments and their alterations.

The Eustachian tube regulates the homeostasis of the middle ear. Problems with its function are predominantly found in childhood. As a consequence, otitis and hearing impairment occur. The most important muscle is the tensor tympani muscle. The complexity of the functional anatomy and physiology are reasons why no function test alone is capable of fulfilling all diagnostic needs. The predictive value of the various Eustachian tube function tests for the outcome of a tympanoplasty is not yet clear. An overview of clinically and scientifically relevant tests for the Eustachian tube function is provided.

Sonotubometry allows an assessment of the Eustachian tube (ET) function under physiological conditions. The reliability of the application of an 8 kHz pure-tone signal was investigated. In 40 normal subjects (80 ears) sonotubometric studies were performed with a custom-made device. ET opening was provoked by swallowing, yawning and Valsalva manoeuvre. An opening was detected in all patients but not in all manoeuvres. Four characteristic sonotubogram types were found. Most common was the spike-type (60%). The double-peak and the plateau-shaped curves occurred in 17% each. The finding of an descendant curve was rare (5%). Of 623 measurements, only in 55% manouvres a positive sonotubometric result was found despite the fact that the patients reported an opening in all cases. The median opening time in dry swallowing, liquid swallowing, yawning and Valsalva was found to be 486, 355, 1,263 and 1,250 ms. A median sound increase of 16.0, 13.8, 15.0 and 15.0 dB was recorded for these manoeuvres. There was a statistic significant difference (P < 0.02) between the increase in sound intensity of liquid and dry swallowing. There was also a statistic significant difference found for the duration of the forced manoeuvres Valsalva and yawning as compared to dry and liquid swallowing (P < 0.0001). The use of an 8 kHz pure-tone signal showed a limited sensitivity for the detection of ET openings. This is mainly due to noise pollution, but also because of an altered positioning and/or dislocation of the probes and compression of the nostrils. The application of an 8 kHz signal is therefore not reliable enough for the use in practice. Further technical refinements and the use of alternative signals are necessary for a broader clinical application.

On the basis of a prediction model for airborne sound insulation (EN 12354-1), a signal processing tool was developed for auralization of indoor and outdoor noise in receiving rooms. For this purpose the direct transmission and four flanking paths were taken into account according to their one-third octave band data. These energy components were addressed to specific field situations in the receiving room with specific delays and directions. The directions of the five transmission paths as well as the reverberation tail were treated binaurally. A large number of building elements can be simulated with nine different hearing rooms. The algorithm was implemented in C (and partly in Assembler). Typical processing time for generation of a 20-s audio file is approximately 10 s on a Pentium II with 233 MHz. Typical time signals, frequency responses, and some sound examples will be presented illustrating this algorithm. This work was done in cooperation with the PTB and supported by Gruenzweig and Hartmann AG.

In the field of nondestructive material testing (NDT), the advantages of a correlation-measuring technique can be used. In particular, the better dynamic range and gain in the signal-to-noise ratio provide a good possibility of investigating strongly scattering or absorbing materials. The ap- plication of maximum length sequences as excitation signals permits the performing of the correlation procedure by using the Fast Hadamard transform (FHT), a very fast correlation algorithm. In nondestructive material testing, a number of special requirements has to be fulfilled. Apart from the driving conditions of the piezoelectric transducers, measurements in NDT often require high measuring frequencies. Based on former developments, a measuring system has been developed that provides a high testing rate; even when using MLS signals of order n=16, a rate of 20 Hz is obtained. A partially parallel calculation structure of the FHT gives a vivid looking presentation of the measuring results.