Automotive Max SPL Test Sequence

A test sequence to measure the Maximum Sound Pressure Level (SPL) of a car infotainment system in the vehicle’s cabin.

Introduction

The sequence measures Automotive Max SPL, the Maximum Sound Pressure Level (SPL) of a car infotainment system in the vehicle’s interior. It calculates a single value for Max SPL and displays the Max SPL Spectrum, showing the six individual microphone responses plus the average curve.

The sequence uses a 6 microphone array mounted at either the driver or passenger locations. A 30 second pink noise stimulus having an RMS level of -12 dBFS is played through the infotainment system and captured by SoundCheck’s Multi-channel Real Time Analyzer (RTA). The Multi-channel RTA produces 6 RTA curves which are then power averaged to produce a Max SPL Spectrum. The spectrum is then power summed to produce a single value for Max SPL.

This measurement method corresponds to that under evaluation by the AES Technical Committee on Automotive Audio (TC-AA). This working group presented a detailed explanation of their work during AES Fall Online 2021. You may view this presentation  courtesy of the Audio Engineering Society (AES).

Required Equipment for Automotive Max SPL Measurement

Hardware

• Listen AmpConnect 621 or similar audio interface with a minimum of 6 inputs. Part # 4046
• 6 x SCM-4 calibrated measurement microphone or similar. Part # 4012
• AmpConnect all-in-one hardware interface Part #4042 OR
• SoundConnect Microphone power supply Part # 4020 AND Power amplifier (SCAmp Part # 4060)

Software

• SoundCheck Plus 19 or later Part # 1102
• 8 Channel acquisition module Part # 2024
• RTA module Part # 2005

Test Setup for Automotive Max SPL Measurement

Automotive Max SPL test configuration

Directions

Hardware Setup & Calibration

1. Connect the hardware as shown in the system diagram below
2. Calibrate each microphone as described in the SoundCheck user manual
3. Place the microphones in the array holder and mount the array in the desired location

Infotainment System Setup

1. Load the WAV file onto the infotainment system using a memory stick or other storage medium
2. Set the system tone controls/EQ to the factory default “flat” settings
3. Set any front/rear, left/right balance controls to the center
4. Set the playback level to maximum

Notes on Software Setup

Auto Hardware is required to be disabled in Calibration. Signal Path gain values should then be entered manually in Calibration and these values will automatically be applied to the RTA Signal Path gains.

Further sequence development

This sequence has been designed for simplicity and to be accessible to most SoundCheck users. Ways in which you could modify or further develop the sequence include:

• Add an autosave step to save sequence data in your desired format
• Add Pass/Fail limits to the final curves and/or values

Get Automotive Max SPL Sequence

Download Sequence (zip file)
Download Sequence documentation (PDF)

Learn more about Automotive Max SPL Measurements.