Acoustic Test and Measurement
We have a well-equipped lab including Head-and-Torso Simulator with Type 4606 handset positioner, fully anechoic chamber, IEC speaker baffle for up to 4" speakers, IEC 318 and 711 couplers, R&D Bluetooth test interface, laser displacement sensor, noise isolated booth with 9 channel diffuse noise simulation, wind noise generator, two pro audio interface data acquisition systems, benchtop electronics, milligram scale, microscope and more. Custom interface cables and patch boxes are often made on-the-spot, and repair of malfunctioning Device-Under-Test (DUT) is typically possible. We use Listen SoundCheck to control many of these items and have written over 150 scripts in-house to measure a huge variety of devices.
Examples of some nifty tests that we can run:
Perceptual Objective Listening Quality Analysis (POLQA) is an algorithm which identifies key metrics of voice quality in degraded speech files. It is a great "one number" metric to compare overall voice performance across multiple devices, or the same device in different conditions- such as background pink noise, restaurant noise, or wind. This can be done at the system level inclusive of Digital Signal Processing (DSP).
A reference-grade point source generates frequency sweeps while a microphone (or mic assembly) is rotated at 5° increments. When the integrated microphone polar, called Directivity Index, is combined with near-field (2.54/10cm) and far-field (0.5-1m) measurements, the Total Noise Cancelling (TNC) metric can be derived, indicative of the ability of a headset microphone to reject background environment noise.
IAR has been performing TIA-810B (narrowband) and TIA-920A (wideband) evaluations on communications devices for a very long time, from analog ringer telephones to bluetooth handsfree devices (shown). We are well informed about current evolutions of this standard such as the combined TIA-920B (2016) series and the impact that has for all digital terminal testing.
Music playback systems often incorporate drivers, algorithms and compression schemes which affect the device's ability to linearly respond to dynamic content. This can make it important to use actual music clips as the stimulus when such a device is under test. Song selections with different crest factors illustrate the objective effects of such "enhancements".
Other tests include:
- Moving-coil loudspeakers and microspeakers (<4” diameter, microspeakers and receivers): 1 meter frequency response, directivity, impedance, Thiele-Small parameters, THD, THD+N, rub and buzz, Two-tone difference frequency distortion
- Headphones and receivers: 318, 711 or 2cc coupler frequency responses and distortion.
- Microphones (ECM and MEMS): frequency response, polar pattern, THD, THD+N, PSRR, Signal-to-Noise ratio, Total Noise Cancelling
- Telephony: TIA-810B/920B, IEEE-269/1329, send/receive, coupling loss
- Wireless and Bluetooth speakers: frequency response, loudness, directivity
- Headphones and earphones: frequency response, level, L/R balance, THD, leak sensitivity
- TV's and All-in-Ones: frequency response, level, balance, THD, directivity
- Far-Field Microphone Arrays: <2m frequency response, directivity, array SNR. Simulated "Classroom" environment measurement.
- Laptop/Ultrabook/Tablet: frequency response, speaker polarity, level, balance, THD, directivity
- Electrical Audio devices (Mic pre-amps, audio interfaces, sound cards): voltage transfer function, input or output impedance, THD