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Voice Coil: March 2021 Article

3/1/2021

 
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Indy Acoustic Research collaborated with Listen, Inc. to bring the data behind the article "How to Measure Free-Field Speaker Response without an Anechoic Chamber" featured in the March 2021 Voice Coil article, linked below!

The hybrid splice method of loudspeaker frequency response measurement compares well with an anechoic chamber for a single loudspeaker if the splice frequency can be determined. However, complex devices require the greater flexibility in setup conditions and off-angle measurements afforded by a full chamber. 
article_vc_mar2021_simulated_free_field.pdf
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3D Printing in-House

3/21/2018

 
To speed iterative prototyping and fixture creation for some assemblies and housings, IAR has brought reliable and low-cost FDM prototyping in-house. Common items we print include speaker baffle adapters, customer housing mockups for probe microphone measurements, or other fixtures to support device assembly or measurements. Maximum print size on this device is approximately 9 x 8 x 8 inches. High-resolution SLA and smaller assemblies will continue to be sourced from a handful of Indianapolis-based prototyping shops.
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Simulation of Microphone Arrays

3/19/2018

 
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 Many far-field voice devices employ beamforming microphone arrays to improve speech recognition and communication performance. However, often the simulation of the acoustic wave during DSP design only includes phase differences due to array spacing and neglects more complex geometry such as element porting, enclosures, tables or walls.  These objects cause diffraction and reflections of the incoming acoustic wave around the sensor can lead to errors in beamforming and direction-of-arrival algorithms. IAR can use Comsol Multiphysics or Lumped Element Simulation (depending upon the complexity of geometry, frequency range of interest and available time) to provide simulated complex acoustic pressure “vectors” to DSP designers to improve the performance of the array including geometric features, prior to any prototype production or PCB fabrication.

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Joint IAR + Listen Talk on Measurements of Cloud-Based Audio Devices

10/18/2017

 
Below is a full copy of the joint IAR + Listen presentation given at the 143rd AES Convention October 21, 2017.  IAR can measure send (microphone) and receive (speaker) responses of "cloud-only" audio devices using Listen SoundCheck software.
aes143_iot_smart_speaker_testing_web.pdf
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Central Indiana AES Visits IAR

3/23/2017

 

Larry Marcus and Marc Reese

The Central Indiana Section of Acoustical Engineering Society (CI-AES) held its March meeting at Indy Acoustic Research LLC with approximately 20 members in attendance.

Humorously dubbed "now for something completely different" (echoing Monty Python), IAR demonstrated the world of embedded audio- where a "large, full-range" speaker is 40 or 50mm diameter. Participants observed testing of voice-controlled virtual assistants in the anechoic chamber, headphone testing in interfering noise in the sound booth and simulation examples of headphone design.
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Glenn explains details of acoustic testing on cloud-based virtual assistants.
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Method for displacement measurement to obtain T-S Parameters

IAR Turns ONE

4/4/2016

 
By: Marc Reese and Larry Marcus
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Indy Acoustic Research celebrates its first year! 

A lot of effort has gone this year into building our lab's capabilities to ensure we can support our customer's needs and timing. Below are some pictures of some of our activities in the past few months.
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Indy Acoustic Research now has the capability to measure speaker displacement directly though a non-contact laser.
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We're just baffled! An IEC-60268 spec baffle allows for testing speaker components up to 3" diameter.
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Simulation improvements have been made for leaky ear models (4195, shown), Transmission Line models of circular and rectangular tubes and radiation patterns of loudspeakers.
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Perceptual Objective Listening Quality Analysis (POLQA) testing on HATS in a customer-defined diffuse noise profile requires that SoundCheck, DAW and POLQA software are run simultaneously
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One of the annoyances in the venerable B&K 4128 HATS is that the chin clip for holding the mic splits due to the stress concentration from inserting the mic. A fuse clip costing less than a dollar is an economical fix with no measurable change to the acoustic field.

Polar Plots Using Excel Radar Chart

10/14/2015

 
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​Excel is a great tool for engineering data reporting due to its widespread use. However, it has never supported a good polar plot which is an essential plot type in multiple engineering disciplines, including acoustics.  The major workarounds I’ve seen are to either download a plugin (which is difficult if you don’t have admin rights) or convert (theta,R) into x=R*cos(theta) and y=R*sin(theta) and use a scatter plot. However, the latter method can take up a lot of spreadsheet space -especially if you have multiple sets of data.
 
It turns out the chart type that you always thought should be able to plot a polar – the Radar Chart – CAN do it; however, there is still some frustration with the formatting of axes. Thankfully, if you work through the frustration once and save the completed chart as a template, it’s much easier to reuse future data sets. See the below attachment for instructions using Excel 2016. There are some differences with older versions, but hopefully you can follow along also...
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iar-_polar_plots_in_excel.pdf
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Diffuse Field Booth

9/18/2015

 
The Diffuse Field Booth is a large audiometric booth and features 8 pro-audio surround speakers and one subwoofer. This setup is calibrated per IEEE 269 to accurately simulate a diffuse noise field, so it's perfect for testing the noise rejection of headset or handset microphones, or noise isolation of headphones (either passive or active noise-cancelling types).  
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HATS in the simulated surround field.

New LAB=OLD LAB

7/20/2015

 
IAR has moved back into the old lab!  The lab has a fully anechoic chamber for far-field devices, Head and Torso simulator (HATS) for near field devices and diffuse field booth for noise isolation measurements. And yes, some desk space for sippin' coffee.
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It's been home for a while, but the gang is now proud to have their own anechoic chamber
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