Blocked ports make a speaker quiet, and a hand makes it loud again
A phone speaker is a tiny driver in a sealed rear chamber, pushing air out through a row of holes. Those holes are not decoration: together with the air in front of them they form the coupling between the diaphragm and the room. When the row fills with a mat of lint, skin oil and dust — which is what pocket fluff becomes after a few thousand hours of the diaphragm pumping air through it — the front chamber stops being open to the world. The diaphragm still moves, but it has almost nothing to push against, so the output collapses and the bass disappears first. What is left sounds thin and quiet.
And that produces the best test on this page, which also feels like a magic trick: cup your hand over the bottom of the phone and the sound gets louder. Your palm closes the gap around the blocked holes and gives the diaphragm a larger surface to couple to, restoring a little of what the lint took away. A driver that is genuinely failing does not get louder when you do that — it sounds the same, or worse. So the hand test separates a cleaning job from a repair in two seconds.
The reason this matters is that the two obvious remedies are both harmful. Blowing into the port drives the mat of lint deeper against the mesh, and adds moisture from your breath to set it. Poking with a pin, a toothpick or a SIM tool is worse, because the mesh sits less than a millimetre above the diaphragm and you cannot see what you have just done. Compressed air is the third: too much pressure drives dust into the housing, and a tilted can spits propellant onto the mesh.
Three faults, three answers
Quiet and muffled, louder with a hand cupped over it, is lint in the ports. A dry soft toothbrush, swept along the row rather than pressed into it, takes off the loose layer. Then a lump of sticky gel — the kind sold for cleaning keyboards — pressed onto the holes and lifted off, repeatedly, with a fresh lump when it gets dirty. That is the step that actually pulls the felt out. Finish with a low-frequency tone: a 180 Hz sine at moderate volume for a minute or two vibrates the remaining dust loose so the next gel pass can take it. Music is worse for this than a pure tone, because its amplitude keeps changing.
No sound at all is rarely the port. Check the obvious first: silent mode, a Bluetooth device still connected, Do Not Disturb, or a per-app volume that got turned down. Try another app, restart the phone, and test speakerphone against the earpiece — if calls are fine and media is silent, you are looking at a software routing problem rather than a driver. If it is silent everywhere and the phone has been wet, stop here: that is a workshop job, and further probing risks the water-resistance seals.
Crackling or buzzing on loud parts means the diaphragm is distorted or something is sitting on it. Cleaning may help if the foreign body is on the mesh side; if the rattle survives a clean, the diaphragm has deformed and only a replacement driver fixes it. On most modern phones that means opening the device, which is worth doing only if the phone matters to you for other reasons.