Posts

100 Things #42: Measuring Max SPL of a Vehicle Infotainment System

SoundCheck is ideal for making in-car measurements such as Max SPL, frequency response and distortion. In fact, SoundCheck is the only full-featured audio test system that offers true nth octave real-time multichannel analysis of 6 microphones simultaneously, that we need for some in-car measurements.  In this short video we demonstrate how we can make Max SPL measurements using a 6 microphone array with SoundCheck and an AmpConnect 621 audio interface. You could make these measurements as part of an end-of-line QC test, in the R&D lab, or to compare various car infotainment systems.

In-Car Max SPL Measurement

Learn More About Automotive Measurements

Watch our Automotive Measurement Seminar in which we make in-car measurements of Max SPL, Frequency response and Buzz, Squeak & Rattle.

Read a short article about the work that the AES Technical Committee on Automotive Audio is doing on Max SPL measurements.

A free pre-written SoundCheck test sequence is available to measure both the Max SPL Spectrum and a single, power averaged value for Max SPL in line with the AES TC-AA working group’s proposed guidelines.

A comprehensive resource on in-car Max SPL measurements is the Audio Engineering Society Technical Committee on Automotive Audio (TC-AA). Their in-vehicle measurements white paper (draft) aims to define repeatable and defined car audio system measurements and in addition to the measurement methods, contains information on standardized test configuration, for example microphone and seat positioning.

Main webpage on SoundCheck for Automotive Measurements.

 

Video Script: Measuring Max SPL of a Vehicle Infotainment System

Did you know SoundCheck can make in-car measurements such as Max SPL, frequency response and distortion? In fact, SoundCheck is the only full-featured audio test system that offers true nth octave real-time multichannel analysis of 6 microphones simultaneously, that we need for some in-car measurements.  In this short video I’m going to demonstrate how we can make Max SPL measurements using a 6 microphone array with SoundCheck and an AmpConnect 621 audio interface. You could make these measurements as part of an end-of-line QC test, in the R&D lab, or to compare various car infotainment systems.

In this test, we use a 6 microphone array to represent the driver’s head. We mount it on a tripod so that it’s easily adjusted to the position where the head would be.

This is placed in the driver’s seat of the car, with the tripod legs as far back on the seat as they’ll go, right against the backrest. The height and angle of the seat are set to the minimum or lowest position. The AES is working on a proposed standard for this type of measurement that defines some very specific dimensions between the pedal and backrest, the height of the stand, and the inclination of the back rest. For this demo, I’m not going to be that precise, but as you can see, I am making sure that I have recorded the dimensions I am using, and the mic array is in a fairly typical driver head position.

Now let’s measure Max SPL. We’ll use broadband monophonic pink noise and we’re going to crank the volume to the max   – even outside of the car this is going to be loud!

It’s hitting 110 dB and we’re going to play it for 30 seconds and take the linear average or Leq. Here you can see the readings on the six microphones, and the black line representing the spatial power average. The test sequence is calculating the overall Max SPL as 111 dB C weighted, and also displays the Max SPL spectrum from 20Hz to 20 kHz.

If you’d like to learn more about in-car measurements, check out our automotive measurement seminar, in which we also demonstrate frequency response and distortion measurements. You can find this in the audio measurements playlist on our Youtube channel! This test sequence that I just used for measuring Max SPL is also available for download, free of charge, from our website.

 

Triggered Record Using WAV File and 6 Mic Array

This sequence allows you to measure a playback system without analog inputs using a 6 microphone array. Specifically, the sequence is designed to measure an in-car audio system. A stimulus WAV file is created in SoundCheck and transferred to the device under test (DUT) where it is played back and the response captured by SoundCheck using a triggered record function. The 6 recordings are batch analyzed to produce individual fundamental curves and the curves are post-processed to produce a single average curve from which an average sensitivity value is calculated.

More