You have not stated over what distance you wish to send your signal.

Your next step is to experiment with infra-red (IR) transmitters and detectors. This would give you less sensitivity to ambient light.

For a more advanced project you can go with a digital solution.

 

a short piece of opaque tubing with the recieving diode inside might help block noise from the sides. a plach sheet of construction paper with the transmit diode sticking through might also help the noise.

 

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The input is also high-pass filtered via C3 and the parallel combination of R5 and R6. The time constant is therefore about 0.57 sec which corresponds to a cutoff frequency of about 0.28 Hz. So your audio signal is getting heavily attenuated. For decent musical audio you want a cutoff frequency in the 15kHz to 20kHz range, so if you use a 10uF cap that will raise your cutoff frequency to about 13kHz, which would be a huge improvement. If you reduce the resistors to about half their current size that will get you into the 20kHz range.

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Some errors there.
The time constant 0.57s for a high pass filter corresponds to about 1/(0.57*2*pi) ~ 0.28Hz . It won't attenuate audio frequencies at all.
Changing 470uF cap to 10uf will raise this to about 13Hz

 

I also changed the 470 uF capacitor to 10 uF but the sound is not as louder as the previous.

Scratching head... "Aha" moment.

That's because I screwed up. This is a high pass filter so you want the cutoff frequency to be below the audio band. My bad.

 

Some errors there.
The time constant 0.57s for a high pass filter corresponds to about 1/(0.57*2*pi) ~ 0.28Hz . It won't attenuate audio frequencies at all.
Changing 470uF cap to 10uf will raise this to about 13Hz

Yep. You are absolutely correct -- when I mess up I mess up good.

It would still seem like 10uF would work better than 470uF, but that's not what the TS observed.

 

First of all, what is the distance over which you wish to transmit your sound?
How much power do you want from the speaker?

For me, a distance of 25 inches or more would be good and I would not prefer a small distance such as 1 or 2 inches .
I can't tell how much power I need but I need a sound which anybody in the room can hear it (small room). I don't know if a transistor can achieve it but I think LM386 gives me enough distance, and loud sound.