Wolfgang Ahnert

Large-area acoustic radiation system

The invention relates to acoustically radiating randomly large rooms and surfaces according to propagation time principles, whereby action or representation and reception or listening areas border directly on one another or are identical. Its object is to avoid error locations and skipping effects caused by movements, which are especially interfering for important solo sound sources. The resulting object of realizing a propagation time staggering without limiting source areas, and responding to the acoustic capacity of the sources, is solved by means of a control device connected to the delay or amplification devices, and which differentiatedly controls them analogous to the sound paths between the source and the acoustic radiator locations.

Acoustics for Auditoriums and Concert Halls

With musical or spoken performances in auditoriums and concert halls, acoustic evaluation is mainly based on the subjective perception of audience and performers. These judgements are generally not based on defined criteria, but characterize the sensed tonal perception. Besides the secondary factors influencing the overall acoustic impression like, for instance, comfortableness of the seats; air conditioning; interference level; and optical, architectural, and stylistic impression, it is especially the expectation of the listener that plays a significant role for the acoustic evaluation. If a listener in a classical concert is sitting next to the woodwind instruments but hears the brass instruments much louder, even though he cannot see them, his expectations as a listener, and thus the acoustics are off. Numerous subjective and objective room-acoustical criteria were defined and their correlation determined in order to objectify these judgments. However, these individual criteria are closely linked with each other and their acoustic effects can neither be exchanged nor individually altered. They become effective for judgment only in their weighted totality. The judgment of the performers, on the other hand, can be regarded as a kind of workplace evaluation.

Latest development in modern measurement tools.

Although personal computer‐based and hardware‐based acoustic measurementsolutions are already available for decades, recently a new, significant development direction emerged. The abundant availability of computing power on personal computers and on mobile devices, such as cell phones, has enabled new ways of making and evaluating measurements. We introduce a set of new tools that exploit these possibilities. The spectrally selective accumulation filter provides a robust means to work in noisy measurement environments or with discontinuous excitation signals such as speech and music. Transferring measurement results to a handheld device, like the Apple iPhone, allows for walking through a venue and evaluating electro‐acoustic and room acoustic quantities easily and at any position. Nowadays, software‐based measurement tools also increasingly replace proprietary hardware‐based solutions, such as for determining the absorption, transmission, and scattering properties of acoustic materials as well as for processing measurements taken in physical scale models.

Measurements and verification of two mosques in Saudi Arabia

Two prestigious mosques, Holy Haram in Makkah and Prophets Mosque in Medinah, have been selected to investigate their acoustical properties. With portable measurement setup basic parameters like reverberation time, intelligibility numbers, sound level distribution, and others have been measured. This was done with and without a sound system installed at the site. In postprocessing the results have been compared with recommendations developed by us for different mosque sizes. Also, proposals are given for further improvements in the existing sound quality. Finally, suggestions for future newly constructed mosques are derived.

New sound system design in concert halls

In 2017, two concert halls have opened in Germany, in January Hamburg’s Elb-Philharmonic Hall and in Dresden the concert hall inside the existing Kulturpalast. The presentation will report briefly about the history and development of both projects. The sound systems in both halls must serve as an announcement system but also in case of emergency as a Speech alarm system according to the German standard DIN VDE 0833-4. For both halls, the target values of Speech Intelligibility have been developed and the design approach for the needed sound systems is explained in the presentation, not only for the halls but for the partially complicated lobbies too. The excellent architectural design of the two halls led to many problems to ensure the required performance of the speaker systems, but to hide their physical visibility. An influential issue was here the interaction with the existing room-acoustic parameters in both facilities. With high reverberation values and expected high noise floors in case of emergenc...

Modern enhancement systems substitute room acoustic design

The acoustic properties of halls and theatres are traditionally achieved by the acoustic design regarding primary shape and secondary structure of interior design. Until now acousticians regularly use their experience and additionally various tools for predicting the acoustic properties of the acoustic design: Physical scale model measurements and/or since the 1990 ties computer simulation as a standard method now. The acoustic properties are evaluated later subjectively by visitors and objectively by engineers with the means of specially developed measures. Parallel to this traditional approach electronic enhancement systems have been developed allowing e.g. a multipurpose hall to convert into a space for concert performances. Since the 1970 ties different systems with different technical approaches have been developed, and it could be said that today electronically generated acoustic properties in halls can be achieved in highest quality satisfying both musicians and audience. After a short overview of ...

Subwoofer array modeling and optimization

In the last few years, configuring subwoofer arrays in order to achieve a desired sound radiation pattern has become one of the most discussed topics in the sound reinforcement industry. The directivity of such arrays of low-frequency loudspeakers can typically be controlled by means of delay, gain, and polarity settings applied to the individual elements. A new software solution is presented that allows modeling and optimizing such setups, including various cardioid configurations as well as end-fire and steered setups. Frequencies down to 20 Hz can be investigated. It is also explained how coherent sound superposition at low frequencies and incoherent interaction of sound waves at high frequencies can be simulated consistently by means of a cross-over frequency band. Finally, an optimization method is presented that allows computing elemental delays automatically based on a user-defined coverage angle for the array.

Acoustic feedback considerations in simulations of sound systems in rooms

Computers are employed since about 30 years in the simulation of room- and electro-acoustics. Simulation tools have always considered sources, usually loudspeakers, but not microphones, which is the reason that acoustic feedback has not been considered by any simulation tool yet. As a new feature, a database for microphones is introduced analogous to the database of loudspeakers and other general sources. It is possible in this way to simulate the regeneration of sound over the close system loop, and estimate the maximum gain before feedback, and related influence on maximum sound pressure level and speech intelligibility. The paper briefly describes the important features of the new microphone database. Afterwards, the basic mechanism of acoustic feedback is explained, and the dependence of the feedback threshold of different sound sources and receivers as well as the acoustic properties of the room. By calculating the feedback threshold the headroom of the acoustic gain before feedback may be predicted....

The national opera theatre in Bucharest—Update of the room-acoustical properties

After the destruction of the old opera house in WWII, the new edifice was designed in 1952–1953. The hall and the pit was almost not changed over the time, so based on the original design the hall acoustics was like in classic opera house not very lively, i.e., very dry. Also, the mutual hearing of the musicians in the pit and between the singers on stage and the musicians was not good. The facelift of the hall involved significant changes of the orchestra pit. A new lift has been built, and the cover of the musicians in the pit has been reduced. Also, the secondary structure of all wall and ceiling parts in the pit has been modified. The same has been done in hall, the carpet in the stalls, and the galleries has been substituted by a parquet floor, the absorbing materials in the boxes, and other wall parts was exchanged by wood panels and the completely absorbing chairs have been changed to less absorbing ones. Acoustic measurements have been done before and after the refurbishment. The paper will descri...

Extended tools for simulated impulse responses

To calculate impulse responses is already done since more than 25 years. The routines did allow simple calculations without and now always with scattered sound components. Today, sophistic routines calculate frequency-dependent full impulse responses comparable with measured ones. Parallel to this development, auralization routines have been developed first for monaural and binaural reproduction and nowadays ambisonic signals are created in B-Format of first and second order. These signals make audible during the reproduction in an ambisonic playback configuration the distribution of wall and ceiling reflections in computer models in EASE. Beside the acoustic detection of desired or unwanted reflections, which always is asking for the correct reproduction of the ambisonic signals the visualization of the reflection distribution is desired. In EASE, a new tool has been implemented to correlate the reflections in an impulse response with their position in a 3D presentation. This new hedgehog presentation of...