v3.1, 200400408, ME
Session R Tuesday, May 11 13:00 h15:30 h
INSTRUMENTATION AND MEASUREMENT
Session Chair: Ian Dennis, Prism Sound, Cambridge, UK
R-1 Evaluation of Objective Loudness MetersGilbert Soulodre, Communications Research Centre, Ottawa, Ontario, Canada
There are many applications where it is desirable to objectively measure the perceived loudness of typical audio signals. The ITU-R is investigating suitable objective measures (meters) that would allow the perceived loudness of various program materials to be equalized for broadcast applications. Ten objective loudness meters were submitted for formal evaluation by several private companies and research organizations. The loudness meters were evaluated for their ability to predict the results of an extensive database derived from a series of formal subjective tests conducted at five test sites around the world. The performance of the various loudness meters is compared and rated using several newly proposed metrics. Several basic objective loudness measures were also evaluated.
R-2 Simulation of the IEC 60711 Occluded Ear SimulatorSøren Jønsson, Bin Liu, Andreas Schuhmacher, Lars Nielsen, Brüel & Kjaer, Skodsborgvej, Denmark
Ear simulators are standardized devices used for calibration of, e.g., earphones and telecommunications equipment. In this paper the ear simulator B&K Type 4157 is investigated using a combined boundary/finite element model (BEM/FEM) of the air inside. Traditionally lumped parameter models have been used to create an electrical equivalent diagram for simulating acoustic impedances. However, these lumped parameter models have some built-in limitations and may not be valid for higher frequencies where the acoustic wavelength is in the range of the ear simulator dimensions. A more accurate acoustic model can be derived using well-established techniques like BEM and FEM. Here we present a combined BEM/FEM model, taking into account the thermo-viscous effects which are shown to be required for obtaining realistic results. Comparisons between simulation and measurements are given.
R-3 High-Performance Wideband Ultrasonic Sell-Transducer Jürgen Peissig, Vladimir Gorelik, Rainer Wiggers, Sennheiser Electronic, Wedemark, Germany
The ultrasonic (US) transducer based on Sells principle is well known to work invertibly as microphone and loudspeaker with a broadband frequency response. US transducers are used for movement and distance sensors, flow-meters, and in parametric transducers where it is important to have a high US sound level in air and good directivity. Driven by these applications we developed several versions of Sell transducers with optimized backplate structures for high sound pressure levels, minimum loss due to the membrane suspension, optimal drive of the membrane surface, and high directivity. Different membrane materials and vent openings result in different frequency responses. The transducer design, its acoustical performance, and the applications will be discussed.
R-4 Enhancements for Loose Particle Detection in Loudspeakers Pascal Brunet, Steve Temme, Listen, Inc, Boston, MA, USA
During loudspeaker production, particles may become trapped in the loudspeaker motor and voice coil vicinity, resulting in a distinctive defect that is easily heard but difficult to detect by traditional test and measurements. We found that a sine sweep stimulus followed by a high pass filter and RMS envelope analysis efficiently detected loose particles and rub-and-buzz defects. The remaining problem is how to reduce the effect of background noise and get more reliable results. Statistical descriptors such as Crest Factor, Skewness, and Kurtosis are first investigated. Experimental results are given and the different tools are compared. New enhancements are described that effectively increase the overall immunity to background noise and discrimination of the method.
R-5 Merging Room-Acoustic and Electro-Acoustic Measurement MethodsWolfgang Ahnert, Stefan Feistel, Waldemar Richert, Software Design Ahnert GmbH, Berlin, Germany
Today various acoustic measurement methods are used to investigate rooms or devices. For room-acoustic measurements MLS routines are often applied to obtain the detailed data according to ISO standard 3382. Instead of MLS, nowadays the dual-channel FFT method based on a sweep stimulus is also commonly accepted. On the other hand, excitation by continuous noise or shot noise is used to obtain a good overview in a short time. For loudspeaker data acquisition or commissioning tests in noisy environments a TDS sweep measurement is performed to achieve results of high accuracy. Here a new measurement tool will be presented, incorporating all of these widely known methods. The advantages and disadvantages as well as the limitations will be discussed for each technique by means of specific examples and measuring applications. A detailed comparison will be provided and recommendations for the practical use under selected acoustic environmental conditions will be given.