3Hz

3Hz is a unit of frequency that represents three cycles per second. In physical terms, one cycle refers to a complete oscillation of a periodic event, such as the vibration of a string or the oscillation of a pendulum. Thus, an object vibrating at 3Hz completes three full oscillations every second. The SI derived unit for frequency is the hertz (Hz), where 1Hz equals one cycle per second, so 3Hz is directly equivalent to 3 cycles per second. In terms of power, a sinusoidal electrical signal at 3Hz has an average power proportional to the square of its amplitude and the frequency itself, though the hertz value alone does not convey amplitude or impedance information.

In acoustic contexts, 3Hz falls within the very low frequency range of human hearing. While the typical human hearing range is roughly 20Hz to 20kHz, frequencies below 20Hz are subaudible to most listeners but can be felt as vibrations. Musical instruments rarely sustain a steady tone at exactly 3Hz; however, some deep resonance phenomena, such as the low-frequency hum of large bass drums or the fundamental vibrations of massive wind instruments, can produce partial components near this frequency. In physics experiments and seismic monitoring, a 3Hz oscillation might correspond to slow, deep earth quake waves or low-frequency seismic noise.

In engineering and electronics, 3Hz is often used as a reference for low‑frequency signal generators and test equipment. For example, a function generator may produce a sine wave at 3Hz to calibrate audio amplifiers or to induce specific mechanical vibrations in precision machinery. In control systems, a 3Hz oscillator may serve as a clock signal for low‑speed digital logic, allowing certain processes to operate with extended periods for fine‑grained timing. The frequency is also used in data acquisition systems to sample slow physiological signals such as heartbeats or slow oscillations in brain activity.

Certain biological and physiological phenomena exhibit processes at or near 3Hz. For instance, the limbic system's theta rhythm in the hippocampus can have components around 4–8Hz, while deeper brain oscillations (delta waves) in sleep can fall in the 0.5–4Hz band, occasionally peaking near 3Hz during deep non‑REM sleep. In neuromotor studies, tremor frequencies can range from 3Hz upward, making this frequency a threshold for distinguishing pathological tremors from normal physiological oscillations.

Overall, 3Hz represents a low-frequency oscillation that finds applications across physics, engineering, music, and physiology. Though it is too low to be heard clearly by most humans, it is a useful reference point for scientific measurement, mechanical testing, and the study of slow dynamic processes in both manmade systems and natural phenomena.