The article is co-authored by Ismail Mohamed.
Ambiance matters! Based on the acoustics of the ambiance, a moderately good sound system can provide a great experience and great speakers may sound awful!
The sound experience can be enhanced by adjusting the position of the speakers or subwoofers or by adding an element to the ambiance, such as a luxurious fancy rug in front of the sound source. Such treatments, however, are not feasible inside a car cabin.
The viable option is to enhance the sound experience with a purely software-based solution that processes the sound and converts it into a directional output covering all areas of the vehicle cabin, and producing virtual sound sources independent of the physical speaker locations in the vehicle. This also leads to a reduced bill of materials and shorter development time.
If you happen to visit Visteon's technical centre in Chennai, you may walk past a “theatre-like” room and a lab, where forward car models are tuned for their audio experience. This is Visteon's unique lab dedicated to acoustics. The lab, since 2016, has significantly built capabilities to enhance the listening experience inside the vehicle – benefiting automakers in India and the world.
The Listening Studio
As part of the lab infrastructure, the company has invested in a listening studio – an isolated, noise-proof room, where the spatial experience of the car is created with world-class amplifiers and speakers.
In the studio, the engineers listen to audio in a controlled environment and understand the sound behaviour – how it travels across the room. The immersive surround sound audio environment enables them to replicate the expected behaviour of the audio output inside a car.
The Acoustics Lab
This is where the action happens. Two things happen in the acoustics lab: Sound tuning and Speech tuning.
Sound Tuning: The interior of a car, as a listening environment, poses many challenges to the audio system designer because of constraints such as characteristics of the cabin, speaker positioning, listener location and noise considerations.
The acoustic tuning of the cabin is carried out to enhance the end-user experience using:
- Objective Evaluation: Parameters of the sound such as frequency response, distortion and acoustical impulse response are measured in different settings: volume, bass, etc. Based on the results, corrections are made to the infotainment system.
- Subjective Evaluation: The engineers – as occupants – first experience the sound or music in the listening studio, and then experience the same sound or music inside a car. Based on their observations, they make necessary changes to the infotainment system for tonal precisions, imaging, stage balance, and linearity in the sound to provide an optimal experience.
Speech Tuning: All in-vehicle speech applications including telephony, voice recognition and e-call, require extensive testing, tuning and certification in accordance with international standards.
Visteon optimises and tunes these applications and ensures that hands-free communication complies with ITU-T Series P.1100-P.1120; eCall feature complies with ITU-T P.1140, and ICC enhancement complies with ITU-T P.1150.
The Visteon team also enhances and optimises voice recognition systems (on-board and off-board) and other VR systems such as Amazon Alexa Auto, Apple CarPlay, etc based on defined standards.
This enables optimal speech quality (by avoiding disturbances related to the vehicle background noise, NVH levels, speaker echo, cross talk, etc) for the user inside the vehicle and the listener outside the vehicle.
About the Authors: Aarif Mustafa leads the audio team in Visteon India and Ismail Mohamed, Audio Architect, leads the Acoustics Lab at Visteon India. Both have been with Visteon for nearly two decades and have been part of the journey of transformation.