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Recommended by Marek PawelczykWith the advancement of digital signal processing technologies, consumers are more concerned with the quality of multimedia entertainment in automobiles. In order to meet this demand, an audio enhancement system is needed to improve bass reproduction and cancel engine noise in the cabins. This paper presents an integrated active noise control system that is based on frequency-sampling filters to track and extract the bass information from the audio signal, and a multifrequency active noise equalizer to tune the low-frequency engine harmonics to enhance the bass reproduction. In the noise cancellation mode, a maximum of 3 dB bass enhancement can be achieved with significant noise suppression, while higher bass enhancement can be achieved in the bass enhance mode. The results show that the proposed system is effective for solving both the bass audio reproduction and the noise control problems in automobile cabins.

Visual and audio cues play very important roles in 3D media. In such media, 3D sound effects allow game developer or a movie director to position sound effects potentially anywhere in a virtual space surrounding the viewer. Hence, accuracy of 3D sound is critical to prevent any degradation of the overall 3D experience. While there are many breakthroughs in the display technology, 3D visual content is still delivered with the current audio systems, which does not accurately deliver 3D sound. This limitation is directly linked to the dispersive nature of the conventional loudspeaker, and the reproduced 3D sound may be perceived to lack sharpness in the spatial imaging due to reverberant nature of the room acoustics. For a directional loudspeaker, the reproduced 3D sound may seem to lack spaciousness due to little influence by the room acoustics. Since most of the loudspeakers in existing sound system are dispersive in nature, 3D audio image tends to be degraded. To solve this problem, we propose a unique setup which comprises of conventional and directional loudspeakers. This setup exploits high directivity of directional loudspeakers to recreate a high quality 3D sound and to recreate the spaciousness of the audio using the conventional loudspeaker.

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Human auditory system does not perceive the sound signal of all frequencies with equal loudness. Based on equal loudness curves, it is known that a low-frequency signal needs to be produced with a higher-power level to have the same loudness as the middle frequency part. There are two ways to overcome this problem; either boosting the power of the low-frequency part or utilizing the psychoacoustics effect called the missing fundamental. There are many works which have been done utilizing psychoacoustics to enhance the low-frequency perception of audio signal. These works are implemented to normal audio systems. Normal audio systems are comprised of a loudspeaker as the audio reproduction end. It is proposed to implement the low-frequency enhancement to a parametric array loudspeaker. The use of a parametric array loudspeaker to generate highly directional audible signal has been reported in several literatures. However, this audible signal lacks low-frequency content. One of the reasons is the relatively low-power level produced by the existing parametric array. By utilizing the nonlinearity property of the air itself, it is proposed to psychoacoustically enhance the perception of the low-frequency part.