A database of acoustic radiation patterns was recorded, modeled, and analyzed for 41 modern or authentic orchestral musical instruments. The generation of this database included recordings of each instrument over the entire chromatic tone range in an anechoic chamber using a surrounding spherical microphone array. Acoustic source centering was applied in order to align the acoustic center of the sound source to the physical center of the microphone array. The acoustic radiation pattern is generated in the spherical harmonics domain at each harmonic partial of each played tone. An analysis of the acoustic radiation pattern complexity has been performed in terms of the number of excitation points using the centering algorithm. The database can be used both for studying the radiation of musical instruments itself, as well as for the implementation of radiation patterns in room acoustical simulations and auralization in order to obtain a spatial excitation of the room closer to reality.

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The directivity pattern of an acoustic source describes the manner in which the sound radiates from it in the spatial domain. It may be used in virtual reality applications to improve the sense of realism perceived by the user. This work presents a directivity pattern database of 41 historical and modern orchestral instruments. The generation of this database includes the recording session in an anechoic chamber using a surrounding spherical microphone array, followed by a preliminary stage of isolating steady parts from the raw signals. Then, calibration is applied by normalizing the signals with the electrical channel gains and with the microphone gains. The fundamental frequency and overtones are then detected and the energy at each harmonic is saved for each played tone. Source centralization is applied in order to align the acoustic center of the sound source to the physical center of the microphone array. Last, a directivity pattern is generated in the spherical harmonics domain for each third-octave band by averaging the directivity pattern at all the overtones with a frequency belongs to that band.

In a series of measurements, the sound power of 40 musical instruments, including all standard modern orchestral instruments, as well as some of their historic precursors from the classical and the baroque epoch, was determined using the enveloping surface method with a 32-channel spherical microphone array according to ISO 3745. Single notes were recorded at the extremes of the dynamic range (pp and ff) over the entire pitch range. In a subsequent audio content analysis, audio features were determined for all 3482 single notes using the timbre toolbox. In order to analyze the relative contributions of timbre- and amplitude-related properties to the expression of musical dynamics in different instruments, Bayesian linear discriminant analysis and generalized linear mixed modelling were employed to determine those audio features discriminating best between extremes of dynamics both within and across instruments. The results from these measurements and statistical analyses thus deliver a comprehensive picture of the acoustical manifestation of “musical dynamics” with respect to sound power and timbre for all standard orchestral instruments.

Teachers belong to the group of professional voice users who often suffer from voice disorders. One reason for a significantly increased prevalence of voice problems can be poor room acoustical conditions in the classrooms. In this study, four rather reverberant and loud classrooms in a primary school in Aachen were analyzed using measurements of the reverberation time, T20, and the speech transmission index, STI. About half of the school’s teachers were investigated with respect to their voice status by using phoniatric, logopedic, and objective voice analysis methods. The prevalence of voice problems in this group was found to exceed previous studies where subjective voice quality was rated. In a second part of this joint project the change of voice quality during the teachers’ working day was analyzed. Two of the four rooms were acoustically optimized. Members of two groups of teachers with and without voice problems were recorded before and after teaching in either one of the acoustically poor rooms or one of the newly renovated rooms. The preliminary results indicate changes of the voice quality in most subjects with respect to one or more voice parameters. Further studies shall prove the significance of the room influence.