Automotive audio systems operate in highly reflective and acoustically challenging environments that differ significantly from optimized listening spaces such as concert halls or home theaters. The compact and enclosed nature of car cabins, combined with the presence of reflective surfaces—including the dashboard, windshield, and window, creates strong early reflections that interfere with the direct sound from loudspeakers. These reflections result in coherent interference, comb filtering, and position-dependent variations in frequency response, leading to inconsistent tonal balance, reduced speech intelligibility, and compromised stereo imaging and spatial localization. Traditional approaches, such as equalization and time alignment, attempt to compensate for these acoustic artifacts but do not effectively address coherence issues arising from coherent early reflections. To mitigate these challenges, this study explores Dynamic Diffuse Signal Processing (DiSP) as an alternative solution for reducing early reflection coherence within automotive environments. DiSP is a convolution based signal processing technique that when implemented effectively, decorrelates coherent signals them while remaining perceptually identical. While this method has been successfully studied in sound reinforcement and multi-speaker environments, its application in automotive audio has not been extensively studied. This research investigates the effectiveness of DiSP by analyzing pre- and post-DiSP impulse responses and frequency response variations at multiple listening positions. We assess its effectiveness in mitigating phase interference, reducing comb filtering. Experimental results indicate that DiSP significantly improves the uniformity of sound distribution, reducing spectral deviations across seating positions and minimizing unwanted artifacts caused by early reflections. These findings suggest that DiSP can serve as a powerful tool for optimizing in-car audio reproduction, offering a scalable and computationally efficient approach to improving listener experience in modern automotive sound systems.
