dB vs Hz – What’s the difference?

dB (decibels) and Hz (hertz) are units used in different contexts and measure different physical quantities. Here is an explanation of each and their differences.

Table of Contents

Decibels (dB)


Decibels are a logarithmic unit used to express the ratio between two values, typically power or intensity. Decibels are widely used in acoustics, electronics, and telecommunications to quantify sound levels, signal strength, and other power-related measurements.


Sound Level: dB measures the intensity of sound. For example, normal conversation is around 60 dB, while a rock concert might be around 120 dB.

Signal Strength: dB measures the power of electrical signals. For instance, in radio and telecommunications, dB is used to describe gain, loss, and signal strength.

Relative Measurement: dB compares two quantities. For example, a gain of 3 dB means doubling the power.

Hertz (Hz)


Hertz is the unit of frequency in the International System of Units (SI), representing one cycle per second. It measures how many times a periodic event occurs in one second.


Frequency of Waves: Hz measures the frequency of sound waves, electromagnetic waves, and other periodic phenomena. For example, the frequency of middle C on a piano is about 261.63 Hz.

Electronic Signals: Hz measures the frequency of alternating current (AC) in electrical systems. For example, the standard frequency of electrical power in the US is 60 Hz, while in many other countries it is 50 Hz.

Oscillations: Hz is used to measure mechanical vibrations and oscillations. For instance, the frequency of a vibrating guitar string is measured in hertz.

Key Differences

Type of Measurement

  • dB (Decibels): Measures ratios and relative levels of power, intensity, or voltage. It is a logarithmic scale.
  • Hz (Hertz): Measures frequency, which is the number of cycles per second. It is a linear scale.

Context of Use

  • dB: Used in acoustics, electronics, and telecommunications to describe sound levels, signal strengths, and gains or losses.
  • Hz: Used in physics and engineering to describe the frequency of waves, oscillations, and periodic phenomena.

Nature of Units

  • dB: Dimensionless unit, as it represents a ratio.
  • Hz: Has dimensions of 1/time (or t-1).

Example Applications

Decibels (dB)

  • Measuring sound intensity: 85 dB (sound of a busy street).
  • Describing signal strength: +3 dB gain in an amplifier.

Hertz (Hz):

  • Frequency of a musical note: A4 note is 440 Hz.
  • Frequency of AC power: 60 Hz in the United States.


Understanding both units and their applications is crucial in fields like audio engineering, telecommunications, and physics, where precise measurements of sound levels and frequencies are essential.