Synth speaker buzzing while not being pulsed

Hi Everyone!

I wanted to make the speaker play some music in the bathroom whenever the light turned on. My set up is:

9V battery >Power bit> Light sensor>Mp3 player>Speaker

There has been some weird buzzing coming from the speaker even if the lights are off. This generally happens after the lights have been off for some time (around 1-2 hours).
There is also a background buzzing from the speaker even when the mp3 track is playing.

I have tried cleaning the contacts and nothing has changed.

Anyone know what the problem might be?

I recorded the strange buzzing here.
You can hear the buzzing at the beginning when the lights are off.

Thanks in advance for your help!

Hi backatcha @fosskers!

Our forum member @alexpikkert also experienced this phenomenon a while ago. Here is his solution:

Hi @fosskers and @chris101,

I have also built this circuit with battery power-light sensor-MP3 player and Synth speaker to check for unwantes noises… :scream:
I could not detect strange noises in the beginning, it all sounded crisp and clear, so I checked the light source first. When there is a fluctuation in the light it quickly triggers the light sensor, resulting in quickly switching the music ON and OFF…
But then I checked the power supply. It seems that the Synth speaker makes funny noises when the power source drains…
I checked this with a variable power supply and yes, my synth speaker went mad…
So I think if you use a fresh battery or a wall wart power supply (the P3 USB power bit) it will be cured…
See this video, watch the voltage meter to see the voltage drop down from 9 Volt to appr. 3 Volt where the hissing and funny noises start). :loudspeaker:

hi @fosskers,
Are you enjoying undisturbed music in your bathroom now ? :grinning: :notes:

Ah ha! So it was the power source. For now, we’ve switched batteries and we’ll see what happens. Switching off the LittleBits brand is also an option; I’ve noticed that sufficiently complicated circuits didn’t perform well with the batteries, but did fine with wall power.

Thanks for the help.

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