You're washing dishes, the call is important, and you crank the volume so you can hear over the tap. Three sentences into the other person's update, your own voice floats back at you with a half-second delay, like a bad impression of yourself played on a slight lag.
Below a certain volume, nothing. Above it, echo. Every time.
This isn't a network fault and it's almost certainly not your carrier's problem. It's acoustic feedback, and it kicks in at a precise threshold because of how your phone's microphone and speaker are physically arranged.
The microphone is always listening
When you're on speakerphone, your phone's speaker projects the other person's voice into the room while your microphone, sitting a few centimeters away, tries to capture only your voice to send back. At low volumes, the speaker output is quiet enough that the mic essentially ignores it. The signal-to-noise math works out fine.
Push past a certain point, and the speaker output bleeds directly into the microphone. The mic picks up the other person's voice, transmits it back down the line, and the other person hears themselves with a short delay. That's the echo they're complaining about. You usually don't hear it yourself; they do.
The specific threshold exists because microphones have a pickup sensitivity curve. Below roughly 70 to 75 dB of speaker output at the mic's position (which varies by phone geometry), the leaked audio sits below the noise floor the phone's echo-cancellation software is tuned to handle. Cross that line and the leaked signal overwhelms the software's ability to subtract it cleanly.
Why software doesn't just fix it
Every modern smartphone runs acoustic echo cancellation, or AEC. It works by keeping a copy of the outgoing speaker audio and mathematically subtracting it from what the microphone captures before transmission. Apple's implementation runs this as part of the audio processing stack; Android handles it through a combination of the hardware audio codec and the OS audio HAL layer.
AEC works brilliantly within a designed operating range. The problem is that it's calibrated during manufacturing for a specific speaker-to-mic bleed level, and treating it like a universal fix is the software equivalent of expecting noise-cancelling headphones to block a door slamming six inches from your ear. The cancellation model breaks when input exceeds its expected parameters.
At maximum volume, the leaked signal also starts to distort slightly as the speaker driver pushes toward its physical limits. Distortion changes the audio signature, so the AEC's reference copy no longer matches what the mic actually hears. The subtraction fails.
Echo gets through.
Consider Priya and Marcus, two colleagues with the same phone model. Priya takes calls at volume level 9 out of 15 and never hears complaints. Marcus works in a noisy open-plan office and runs his at 14 or 15. His callers report echo constantly. Same hardware, same software, different outcome: Marcus crosses the threshold on every single call.
What you can actually do about it
The most reliable fix is also the least satisfying: turn the volume down. Dropping from maximum to around 70 to 75 percent of the scale on most phones puts you back inside the AEC's working range. If that makes the call too quiet for your environment, earbuds or a wired headset solve the problem structurally, because the mic is now physically separated from the speaker by a meter or more of cable. The leaked audio drops to essentially zero at that distance.
Bluetooth headsets work for the same geometric reason, though they introduce a different variable. Bluetooth audio codecs like SBC or AAC add latency, which can occasionally create a slightly different echo artifact at the receiving end on poor connections. For most calls, Bluetooth is a clean solution.
One question worth asking before you blame your carrier: are you on a video call app rather than a regular phone call? Zoom, Teams, and Google Meet all run their own echo suppression layers on top of the OS-level AEC. Sometimes these conflict and actually make echo worse. Disabling the app-level suppression and letting the OS handle it alone can help.
The fix isn't glamorous and it won't feel like a fix at all, just a small surrender on the volume slider. But your phone's microphone has no idea it's supposed to ignore the speaker sitting two centimeters away, and past a certain loudness, no amount of clever software can convincingly pretend otherwise. Physics, as ever, is indifferent to your kitchen noise.