An equalizer is basically a way to turn certain sounds up or down depending on their pitch. Think of it like adjusting the bass and treble knobs on an old stereo, except way more precise.
Here's a simple breakdown of the frequency zones and what they actually do to your sound.
Deep low end, around 20 to 60Hz, is mostly rumble you can't really hear as music or voice. On phone recordings this is usually just noise from handling the phone or background hum, so cutting it is almost always a good idea.
The bass range, roughly 60 to 250Hz, gives a voice its weight and warmth. Phone mics tend to overdo this a bit, making things sound boomy or thick.
Low mids, around 250 to 500Hz, are where that boxy, muffled sound comes from. If a recording sounds like it was made inside a small closet, this is usually the culprit.
The mid range, 500Hz to 2kHz, is where speech lives. This is the heart of what makes someone sound clear and understandable.
High mids, between 2 and 4kHz, add presence and help words feel crisp. This is the area that makes speech pop instead of sounding flat.
The higher end, 4 to 10kHz, is about air and sparkle. Phone mics often struggle here, which is why recordings can sound a little dull or lifeless.
Anything above 10kHz adds shimmer, but it's also where hiss tends to creep in, so it needs a light touch.
For phone recordings specifically, a few habits go a long way. Start by cutting everything below 80 or 100Hz since it's rarely useful. Trim the boxy area around 200 to 400Hz if things sound muddy. Add a small boost around 3 to 5kHz for clarity, and if the voice still feels flat, a gentle lift around 8 to 10kHz can help, just don't overdo it since phone audio gets harsh fast.
