Increase volume of alarm in countdown timer?
There are three avenues to this:


get a soft toothbrush and make sure the speaker grill is clean and free of debris
position the phone so the speaker echoes/reverberates from a hard reflective surface that channels the sound to your ears.
choose custom alarm tones that are audio compressed and recorded "hot" and perhaps alternate loud/soft as your brain will hear the changes as more relevant than a flat loud monotone