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Extracting urban sound information for residential areas in smart cities using an end-to-end IoT system. IEEE

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.

Studies involving subjective evaluation require feedback from human participants to assess the performance of a system or an environment. A participant is typically presented with a set of metrics to be observed and they present their assessment accordingly. Investigator-led in-situ soundscape evaluation in ISO 12913-2 collects perceptual responses along with other acoustical and locale information. This is a labor intensive and time-consuming processes. To alleviate and complement investigator-led evaluations, a portable and compact feedback system with an e-ink display and capacitive buttons was designed, and is undergoing field tests to address the aforementioned requirements. The system employs a low-cost, low-power microcontroller unit (MCU) with necessary hardware interfaces to enable capacitive sensing. Capacitive buttons provide an intuitive interface and avoid the inherent wear and tear of mechanical buttons. This digitized feedback interface affords the flexibility to synchronize (wired or wirelessly) with a playback system to evaluate an augmented soundscape, and is suitable for both supervised and unsupervised subjective assessments.

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