415Hz

415Hz is a frequency value representing 415 cycles per second. As a pure tone it falls within the audible range for human hearing, with a wavelength of approximately 0.83 metres in dry air at 20 °C.

In electrical engineering 415Hz is a common intermediate frequency used for certain high‑voltage and medium‑voltage power systems. The frequency was historically adopted in many European countries for the medium voltage supply (400 Hz nominal) and remains in use for specific industrial applications such as side‑scanning ultrasound, communication systems and high‑frequency transformers. The standard frequency is defined in the European EN 500 series and in ISO 20060 for EU transmission networks. The 415Hz supply is generally supplied in three phases and is approximately ±3 % offset from the nominal 400Hz.

In music and acoustics 415Hz is sometimes employed as an alternative tuning standard. It is about 23 cents below the normal concert pitch A4=440Hz, giving a slightly lower pitch used by some ensembles that prefer a flatter temperament. Because the difference is small it can be used in crossover designs where harsh high‑frequency content is reduced without major pitch distortion.

Beyond power and music, 415Hz is occasionally used as a reference frequency in scientific experiments that require a stable, low‑frequency signal. Radio communications can use 415Hz as a modulation tone, and ultrasonic transducers may be driven near this frequency for specific diagnostic or clearance measurements.

References to standards such as EN 500 and ISO 20060 contain detailed specifications on the 415Hz system, while acoustics treatises discuss its musical implications.