UPDATE 2016_07_02. The bandpass filter described below does not have sufficient out of band rejection to meet the OP's requirements.
Hi friends
I need a way to detect 10 KHZ sound, I use simple electret microphone with pair of 2N2222 transistors as aplifier, the problem is with other frequency noises on it, i want to filter other sounds below 8 khz and upper than 11 khz, can someone suggest me a filter or circuit?
I use electret microphone because of it's low price, can i use anything instead of microphone?
Regards
Hy Navid,
Welcome to ETO- where are you? Care to tell us a little about yourself- your age, the electronic tools and test equipment you have, your level of expertise in electronics?
As the other members have said, you haven't stated your requirement in sufficient depth for us to do a definitive design, but I have made a few assumptions and posted the circuit below for discussion. The circuit is a band pass filter, which will pass 10KHz but attenuate higher and lower frequencies. Thanks to
Alexander C. Frank, aka อ.ช้างเผือก (Ref 1) for the use of his excellent bandpass filter calculator.
If you need a visual indication that 10KHz is present at the output of the opamp (U1), like a meter or a LED, we can do that.
COMPONENTS
(1) C1, C2: 2n2 (2.2 nano Farads)
(2) R1: 361K72 (361.72 Kilo Ohms)
(3) R2: 723K43 (723.43 Kilo Ohms)
(4) R3: 72R4 (72.4 Ohms)
(5) U1: Texas Instruments OPA192 operational amplifier (opamp)
(6) Power lines: +-15V
DATA SHEETS
(1) OPA192:
https://www.ti.com/lit/ds/symlink/opa192.pdf
BAND PASS FILTER CHARACTERISTICS
(1) Center Frequency (Fc): 10KHz
(2) Bandwidth (BW) @ -3dB: 200Hz
(3) Quality Factor (Q): 50
(4) Gain at Fc: 1
REFERENCES
(1)
https://www.changpuak.ch/electronics/Narrow_Bandpass_2.php
(2) **broken link removed** (paragraph 16.5)