With over 100 combined years of audio measurement experience, our team has created a wealth of technical papers, sequences, articles and other useful information to assist you with your audio test needs. Please browse the collection below, or filter by type of resource.
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Author: Steve Temme
The sine generator in SoundCheck®, operates on the same principles as a traditional swept sine measurement system consisting of a sine generator, voltmeter, tracking filter, and level recorder. The main difference is that it is implemented in the software as a virtual instrument. The SoundCheck sine generator sweeps in discrete steps; each frequency step contains numerous cycles that are synchronously averaged to minimize the effect of background noise. Transducer settling (transient ringing) is also minimized by discarding the first few cycles at each new frequency step and providing a phase continuous transition between frequencies. This provides higher frequency, amplitude, and phase accuracy, as well as excellent noise suppression. Instead of using a tracking filter that can only measure one harmonic at a time, SoundCheck uses a proprietary FFT-based algorithm, called HarmonicTrakTM, which is equivalent to a parallel bank of individual tracking filters that measure all selected harmonics simultaneously. This parallel analysis technique saves considerable measurement time over the traditional serial analysis method.
Author: Steve Temme
Loudspeaker distortion is undesirable. The type and level of distortion, however, can greatly influence the perceived annoyance. In addition, identifying the type of distortion can also help pinpoint the mechanism or mechanisms in the loudspeaker that are causing the distortion. “Rub & Buzz” is a good example of a particularly annoying type of distortion that is very difficult to measure. Pinpointing the cause of the problem from the measurement is an even more difficult task. Understanding why this type of distortion is so annoying and how to measure it is critical in being able to properly test loudspeakers on the production line.
Authors: Steve Temme and Christopher J Struck
Evaluation of loudspeaker performance at low frequencies is complicated by long wavelengths, room interaction and cabinet/baffle diffraction. Since low frequency measurements have traditionally required large, impractical testing environments, different techniques have been developed in an attempt to overcome this requirement. Anechoic chambers, outdoor measurements, half-space measurements, ground plane measurements, cepstral liftering, parametric modelling and near field techniques are compared with respect to accuracy, speed, bandwidth and practical implementation.
Author: Steve Temme
In the never ending quest for better sound transmission, reinforcement, and reproduction, the electronics have been extensively analyzed for distortion. Distortion in the electroacoustic transducers, while typically several orders of magnitude greater, has often been neglected or not even specified because it has been difficult to measure and interpret. With a basic understanding of transducer limitations, some knowledge of human hearing, and the application of different distortion test methods, electroacoustic transducer distortion becomes easier to measure and assess. Note: Although this paper was written over 20 years ago, the principles are still true today.
Author: Martin Rung
A time selective measurement of a frequency response is (directly or indirectly) based on a measurement of the impulse response, where a well-defined time window is applied to the impulse response. The frequency response is simply the Fourier transform of the impulse response. Time selective measurements are often used in electroacoustics to make simulated free-field measurements of transducers. This is to isolate the directly transmitted, “freefield” sound from reflections due to the surroundings. By using a time window applied to the impulse response, it is
possible to obtain results similar to those obtained in a non-echoic environment.
Distortion curves are conventionally plotted under the corresponding excitation frequency of the measured fundamental. Interpretation of results can be misleading due to the influence that the passband shape and amplitude irregularities of the fundamental response have on the distortion responses. By ‘amplitude normalizing’ the distortion responses to the measured fundamental response before plotting them at the excitation frequency, distortion graphs become easier to interpret for diagnostic purposes. In addition, the distortion curves become insensitive to room reflections in the measured responses.
Authors: Steve Temme
Presented at the 94th AES Convention, Berlin, 1993
The development of time selective techniques has enabled measurements of the free field response of a loudspeaker to be performed without the need for an anechoic chamber. The low frequency resolution of both time selective techniques and anechoic measurements is, however, limited by the size of the room. A technique is presented enabling measurements of the complex free field response of the loudspeaker to be performed, without an anechoic room, throughout the entire audio frequency range. It is shown that this technique can also be used for measurements of harmonic distortion.
Authors: Christopher J. Struck and Steve Temme
Presented at the 93rd AES Convention, San Francisco, 1992