my powerbook speakers are over modulating the sound

Do you have a PowerBook (pre-2006) or a MacBook Pro as shown in your equipment profile? Very different computers inside. Please clarify so we can better help you in this text-based setting.

If a MacBook Pro, try resetting the System Management Controller:

Reset the SMC of your Mac - Apple Support

Make SURE yo uknow which generation Macbook Pro you have.

Identify your MacBook Pro model - Apple Support

We need positive identification of you computer before we can offer further help.

Ah! Thanks!

Did you try the SMC reset using the instructions for a Mac with an Interl procero but wihtout the T2 security chip?

If that does not fix it, the speaker may be blown. Although Apple will not work on a computer that old, an independent service person should be able to determine the speakers are damaged and be able to source used/pulled one and install them.

You always have the option of headphones, earbuds, or external speakers if you do not wish to invest in a repair.