Sound, radio, Wi-Fi, sunlight, music notes, brainwaves, heartbeats — all of them are patterns over time. Frequency tells you how many cycles happen per second.
A wave is a repeating pattern. Frequency describes repetition speed; period describes the time for one cycle. Lots of “frequency” talk becomes easy once you can swap between Hz ↔ period ↔ wavelength.
How many cycles happen each second.
Time for one cycle. Relationship: f = 1/T.
Distance per cycle. If a wave travels at speed v, then v = f·λ.
Humans typically hear roughly 20 Hz to 20,000 Hz (20 kHz). Lower frequencies feel like thumps/rumble; higher frequencies feel like hiss/brightness.
These ranges vary by source, but the “feel” of them is widely used in mixing and audio engineering.
Loudness relates to amplitude, often measured using decibels (dB). Frequency is “how often.” You can have:
Push a swing at the right timing and it grows. In audio, resonance can make certain notes jump out.
Light is also a wave — just at wildly higher frequencies than sound. Visible light is roughly in the hundreds of terahertz (THz).
kHz → GHz. Communication, broadcasting, Wi-Fi, cellular.
Higher than radio. Heat radiation sits in infrared.
Visible light is a narrow slice. UV and beyond carry more energy.
In quantum terms, higher-frequency light has higher energy per photon (that’s why UV can cause sunburn). Different parts of the spectrum interact with matter in different ways — which is why we use different bands for different tech.
In computers, we “sample” a continuous wave at fixed intervals. The sample rate is measured in Hz too (samples per second). More samples per second can represent higher frequencies.
To capture a frequency, your sample rate must be more than 2× that frequency. Example: 44,100 Hz audio can represent up to about 22,050 Hz.
If you try to sample a frequency higher than half the sample rate, it can appear as a different, lower frequency. That’s why anti-alias filters exist.
Convert between frequency and period, find wavelengths, and get “what does this feel like?” ranges.
If f is 0, period is “infinite” (it’s not repeating).
Type a frequency and get a quick label (sound bands + EM hints).
Make a wave. Change frequency, amplitude, and phase. Watch the “wiggles” compress and expand.
These are conventional ranges used in EEG discussions.
Notes double every octave: 220 Hz → 440 Hz → 880 Hz. That “doubling” is why pitch feels logarithmic.
Springs, bridges, glass, engines, guitar strings — everything has “natural” frequencies. Engineering often means avoiding unwanted resonance.