I want to make a humming sound at a low frequency - 29Hz. I’m using a 555 timer to generate the sound, a few caps/resistors to turn it into a sine wave, and finally LM386 to amplify the wave. I would connect this to a small cheap speaker (8 Ohm).
I’ve tried simulating the waveform in LTspice, but get very poor results (very low voltage and distorted). The end goal is for the hum to be heard from a few feet away. I’m looking for guidance with this circuit. Do I even need the LM386? Do I need to decouple it (22uF)? Can the speaker be simulated with just a resistor? Any help is appreciated. Thanks
I think you might have better luck with a simple 2 transistor oscillator, rather than the 555 approach, since your end desired result is a low frequency sound (sine wave). Check out the Forrest M Mims book “Engineer’s Mini notebook - Basic Semiconductor Circuits”, page 28, “Audio Oscillator”. (PDF of this can be easily googled). If you want to go the 555 / 386 route, keep any decoupling caps in the signal path large. I can’t view inline attachments in the forum for some reason, but from squinting at the thumbnail, looks like you have a 0.1uf going into the op amp and a .01uf coming out? 29 Hz wants a nice big cap to flow thru, 22uf or maybe larger, and a larger speaker will reproduce this sound better.
