A frequency range is the span between the lowest and highest frequencies that a system produces, detects, or operates within. It’s defined by two boundaries: a lower limit and an upper limit, both measured in hertz (Hz), where one hertz equals one complete wave cycle per second. Whether you’re talking about human hearing, a Wi-Fi signal, or visible light, frequency range describes the window of frequencies involved.
The Core Concept
Any wave, whether it’s a sound wave or an electromagnetic wave, vibrates at a certain number of cycles per second. That rate is its frequency. A frequency range simply captures the full spread from the lowest frequency to the highest. If a microphone picks up sounds from 50 Hz to 18,000 Hz, that entire span is its frequency range.
A closely related term is bandwidth, which is the numerical difference between the upper and lower limits. If a signal occupies frequencies from 88 MHz to 108 MHz, its bandwidth is 20 MHz. Frequency range tells you the actual boundaries; bandwidth tells you how wide the window is.
How Frequency Range Applies to Sound
Humans can detect sounds in a frequency range from about 20 Hz to 20 kHz (20,000 Hz). That said, most adults lose some high-frequency sensitivity over time, and the practical upper limit for the average adult is closer to 15,000 to 17,000 Hz. Infants can hear slightly above 20 kHz before this gradual decline begins.
Other species operate in very different ranges. Some bats are sensitive to tones as high as 200 kHz, but their lower limit sits around 20 kHz, right where human hearing drops off. Sounds below 20 Hz are classified as infrasound, and sounds above 20 kHz are ultrasound. Both exist as real pressure waves; they simply fall outside the human auditory frequency range.
When you shop for speakers or headphones, you’ll see frequency range listed in the specs. This represents the actual span of frequencies the device can reproduce. A speaker rated at 38 Hz to 50 kHz, for example, can produce meaningful sound across that entire span. Manufacturers typically define “meaningful” as staying within a certain loudness threshold, usually no more than 6 dB below the average output. You may also see a “frequency response” spec, which is a related but different measurement. Frequency response shows how evenly (or unevenly) a device reproduces sound across its frequency range, plotted as a curve. A flat frequency response, staying within plus or minus 3 dB, means the speaker doesn’t favor bass over treble or vice versa.
Frequency Ranges in the Electromagnetic Spectrum
Light, radio signals, X-rays, and microwaves are all electromagnetic waves, differing only in frequency. The full electromagnetic spectrum stretches from about 3,000 Hz (very long radio waves) up to 3 × 10²⁶ Hz (the most energetic gamma rays). Each type of radiation occupies its own frequency range within that spectrum.
- Radio waves: 3 kHz to roughly 3 GHz
- Microwaves: 3 GHz to 30 GHz
- Infrared: around 30 THz (30 × 10¹² Hz)
- Visible light: approximately 430 THz (red) to 750 THz (blue/violet)
- Ultraviolet: above 750 THz up to about 30,000 THz
- X-rays and gamma rays: frequencies above 30,000 THz, extending into the trillions of trillions of Hz
Visible light is a tiny sliver of this spectrum. Your eyes are biological sensors with a frequency range limited to roughly 430 to 750 THz, just as your ears are limited to 20 Hz to 20 kHz.
Radio Frequency Bands
The International Telecommunication Union (ITU) divides radio frequencies into standardized bands, each with its own label and frequency range. These classifications matter because different bands behave differently: lower frequencies travel farther and penetrate buildings better, while higher frequencies carry more data but cover shorter distances.
- VLF (Very Low Frequency): 3 to 30 kHz
- LF (Low Frequency): 30 to 300 kHz
- MF (Medium Frequency): 300 to 3,000 kHz, home to AM radio
- HF (High Frequency): 3 to 30 MHz, used for shortwave radio
- VHF (Very High Frequency): 30 to 300 MHz, used for FM radio and television
- UHF (Ultra High Frequency): 300 to 3,000 MHz, used for cell phones and Wi-Fi
- SHF (Super High Frequency): 3 to 30 GHz, used for satellite communications and radar
Modern 5G networks illustrate why frequency range matters in practice. 5G operates across two defined ranges: Frequency Range 1 (FR1), spanning 410 MHz to 7,125 MHz, and Frequency Range 2 (FR2), spanning 24.25 GHz to 71 GHz. FR1 provides wider coverage with moderate speeds, while FR2 delivers faster speeds over shorter distances. The tradeoff between range and data capacity is a direct consequence of the physics at different frequencies.
Frequency Range vs. Single Frequency
A single frequency is one specific rate of vibration, like a tuning fork producing a pure tone at 440 Hz. A frequency range, by contrast, is always a span. Most real-world signals are not single frequencies. A human voice during normal conversation uses frequencies roughly from 85 Hz to 8,000 Hz. A Wi-Fi router transmits across a band of frequencies centered around 2.4 GHz or 5 GHz. In each case, the frequency range captures the full extent of what’s being produced or received.
This distinction matters when you’re evaluating any device or system. A guitar amplifier with a frequency range of 75 Hz to 5,000 Hz will miss both the deepest bass notes and the highest overtones. A radio receiver tuned to a frequency range of 88 to 108 MHz will pick up FM stations but nothing else. The frequency range defines the boundaries of what the system can work with, and everything outside those boundaries is effectively invisible to it.