Improvement of voice quality and prevention of deafness by a bone-conduction device

Figures & data

Table 1. Locations and average noise levels.

Location	Level (dBA)	Location	Level (dBA)
Subway platform	85.7	Shopping mall	78.3
Bus Inside	80.4	Parks	55.1
Subway	80.9	In office	61.2
Road side	77.9

Figure 1. Ambient noise comparison between two places: loud condition (at public transportation, red line) and calm condition (at parks, dashed line).[1,2]

Figure 2. Auditory field.[7]

Figure 3. Block diagram of the bone-conduction system. A: voice signal in an ordinary mobile phone; B: modified signal from bone-conducting speakers (B = A′ + C′ + D); A′: amplified high frequency from received signal; C′: compensated signal of ambient noise phase; C: incoming signal from additional microphone; D: incoming signal from ordinary mobile phone microphone.

Figure 4. Components applied to the bone-conduction system.

Figure 5. Open- and closed-loop frequency responses.

Figure 6. Parameters of frequency modelling.

Figure 7. Comparison of frequency responses between an ordinary phone and a bone-conducting phone.

Figure 8. Comparative analysis before and after the activation of the proposed system.

Table 2. Results from the sensitivity assessment.

Evaluators	Before (dB)	After (dB)	Evaluators	Before (dB)	After (dB)
#1	99	85	#11	97	84
#2	102	84	#12	99	82
#3	98	74	#13	103	83
#4	97	82	#14	99	85
#5	99	83	#15	97	83
#6	103	89	#16	98	84
#7	101	83	#17	103	85
#8	99	81	#18	102	84
#9	98	83	#19	99	86
#10	101	84	#20	105	83
Average	99.95	83.35

Occupational Safety and Health Research Institute (OSHRI). Noise-measurement and evaluation. USA: OSHRI; 2007.

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