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Multimedia

The customer expectation of multimedia and communication systems in a modern vehicle are very high. The sound quality must be good and any features like voice control or hands free must work perfectly. A lot of development is done at the supplier side and the fine tuning is done in the vehicle. Testing includes verification of frequency response, sound field and sound quality and is done both with measurements and subjective evaluation. The entertainment system can also have a secondary task, ANC, active noise control, to reduce powertrain or road noise by creating an antiphase sound and this needs obviously careful tuning. The same active system can also add desirable sounds, to improve engine sound quality at certain driving conditions.

Challenges:
The entertainment system performance is typically something every person has an opinion about. This means that the correlation between the subjective experience and the objective measurements is important. Comparisons between subjective evaluation protocols and measurements for different settings is of course a useful method for the development team to capture the progress. Binaural recordings can also be used for blind tests.
The expected future with autonomous vehicles means that multimedia systems will be even more important to enhance the travel experience.

• Testing time has to be short since the access to prototypes is limited and The cost for wind tunnel testing is very high.
• Instrumentation must be fast and easy in a way to record repeatable results.
• The microphones must be installed to minimize structure borne sound.
• Microphone holders and cables shall not introduce any rattle noise.
• The installation shall be safe for the test engineer during vehicle test.
• Calibration verification must be easy to perform.

The transducers shall survive the sometimes tough life in the NVH laboratory or on road testing. Microphones can accidently be dropped.

Example:
System testing is done in a quiet environment, preferable a hemi-anechoic chamber. Microphone arrays or artificial heads are used for measurements of
the frequency response from the entertainment system and artificial head can also be used for recordings to be used for subjective comparisons. Speed dependent volume and equalization tuning needs to be measured and verified in combination with road noise measurement data.
Evaluation at test driving will be the final verification.

Microphones used to measure frequency response shall be robust. Random microphones with a frequency response of at least 20 Hz – 20 kHz are most often used.