2007年6月13日 星期三

The sound which microphone received is too low 麥克風收到的聲音太小

There are three reason might cause the problems,
1. Lower sensitivity of microphone
The sensitivity of the condenser microphone is from -36 dB to -48 dB (0dB= 1V/Pa). If we use -44 dB microphones, the sound will be lower.
2. Defective design of amplifier
The impedance for the amplifier will affect the sensitivity and the frequency response.
Normally, the higher the impedance is, the better the sensitivity will be. However if the impedance is too high to get enough voltage/current, the high frequency response may get worse.
The lower the impedance is, the lower the SPL will be. The too much current will cause the insufficient voltage.
Input higher voltage will increase the sensitivity. Depend on the design of the amplifier and the frequency, the sensitivity might increases around 0.3 dB to 0.6 dB by 1 V.
3. Defective design of mechanism
The over-length or curved sound receiving holes leads to lower or unnatural sound.
麥克風所收到的音量太小,主要來自於三種原因,
1. 麥克風的靈敏度偏低
電容式麥克風的靈敏度大概介於-36 ~ -48dB之間(0dB=1V/Pa),若採用-44dB的麥克風,則可能收音的聲音會較小,
2. 放大線路設計不良
放大線路所匹配的阻抗,會影響麥克風的靈敏及高低頻的響應,
一般來說,匹配的阻抗愈高,麥麥克風的音量會愈大,但阻抗高到造成給麥克風的電壓/電流不足時,高頻的響應會變差.
阻抗愈低音量愈低,因為電流量太高使電壓不足.
給麥克風的電壓愈高,靈敏度也會增高,增加1V大約是0.3-0.6dB左右(視放大線路設計,頻率有所不同)
3. 機構設計不良
收音孔太長,或是彎曲,都會使收到的聲音變小或不自然,

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