The existing evaluation methods and indexes of noise of electric motors can not comprehensively reflect all the physical characteristics of noise of hub permanent magnet synchronous motors (HPMSM) and human subjective sensations. In this paper, a method of the sound quality (SQ) evaluation of HPMSM for electric vehicles is proposed. The method is divided into three steps. In the first step, a noise objective evaluation of HPMSM with seven acoustical objective indexes, including loudness, roughness, A-weighted sound pressure level (A-W SPL), tonality, sharpness, articulation index (AI) and fluctuation strength, is made. In the second step, a noise subjective evaluation of HPMSM by using the grade evaluation method is made. The subjective annoyances (SA) of noise samples of HPMSM are obtained. In the last step, the SQ evaluation model of HPMSM by using the BP neural network theory is established. The average error rate of the proposed model is only 3.97%. By means of weight analysis, a comparison between the relative importance of acoustical objective parameters is found out. The main original contribution of this paper is that the proposed method can comprehensively reflect all the physical sound characteristics of HPMSM as well as their influence on human subjective sensations.

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Optical mobile communication (OMC) provides a hopeful vision to handle with wireless communication scenarios where multiple mobile users are involved. In previous work, achievable rate analysis for broadcast OMC system with coherent transmission and detection is given. Although it was shown that OMC has superior performance compared with conventional schemes, coherent processing imposes strong challenges on the hardware design. In practice, intensity modulation (IM) and direct detection (DD) is more implementation-friendly. However, the result in coherent processing cannot be migrated to IM/DD scenario since IM imposes new constraints on the signal model, making it more challenging to evaluate the rate performance. Motivated by this, in this paper, we investigate the rate performance of broadcast OMC in IM/DD mode with user mobility. The aim of this work is to reveal the potential gain of OMC with IM/DD over some benchmark schemes. By assuming dense pulse amplitude modulation (PAM), the rate is assessed through mutual information with proposed power allocation algorithm. Through simulation results, it is found that OMC outperforms conventional free space optical (FSO) communication in time division mode at high SNR region with not-so-large number of users.