How to stop that horrible squealing sound from your speaker

Feedback is the howl, screech, or ringing tone that appears when a live mic and a speaker turn into a closed loop. It is not random — it is a measurable physical effect, and most of the time you can stop it without changing apps, gear, or settings.

What feedback actually is

A microphone picks up sound, the system amplifies it, and a speaker plays it out. If the speaker's output reaches the microphone loudly enough, the mic picks up its own output, amplifies it again, plays it out again — and the loop continues. The system locks onto whatever frequency the room reinforces most, which is why feedback always has a specific pitch instead of being broadband noise.

Three variables control whether the loop runs away:

Distance between microphone and speaker (more is better)
Direction the speaker is pointing (away from the mic is better)
Total system gain (input gain plus output volume — less is better)

The placement rules

For a typical iPhone-plus-Bluetooth-speaker setup in a living room, the working rules are:

At least 1.5 m between the phone and the speaker
Speaker pointing away from the phone, ideally toward the audience
Phone held vertically, not lying flat next to the speaker
Avoid hard reflective surfaces immediately behind the phone (a wall, a window)

Most home feedback is solved entirely by this. If you can't get 1.5 m of separation, turn the speaker so the phone is behind it, not in front.

Volume staging

When feedback starts, the instinct is to lower the input gain on the phone. That usually does not help, because input gain rarely goes high enough on a phone mic to drive the loop. The fix is on the output side: lower the speaker volume. Start the speaker at about 30% of its range, raise gradually, and stop a few notches before you hear the room starting to ring.

Bluetooth speakers usually have their own volume independent of the iPhone. Keep the speaker at about 60% and use the iPhone as a fine adjustment — this gives more headroom and a faster cut path when feedback threatens.

When placement and gain aren't enough

Some rooms will feed back no matter what you do — small bathrooms, hard-walled kitchens, anywhere with strong reflections at the resonant frequency of the speaker. In those cases:

Move to a different room with softer surfaces (carpets, curtains, sofas)
Use a directional microphone accessory through Lightning or USB-C — phone mics are omnidirectional and pick up the speaker easily
Switch to wired headphones for monitoring so the speaker can be much quieter (or off) and you still hear yourself

What apps can and can't do

Voice presets and gentle compression help slightly by smoothing peaks. Notch filters at the feedback frequency can suppress one specific tone but typically just move the feedback to the next-most-resonant frequency. Automatic feedback suppression, available in some apps, watches for ringing tones and ducks them — useful, but not a substitute for placement.

The honest order of operations is: fix placement and volume first, use app processing second, change gear last. Most home feedback problems never reach step two.