In telecommunications, a psophometer is an instrument that measures the perceptible noise of a telephone circuit.^[1]

The core of the meter is based on a true RMS voltmeter, which measures the level of the noise signal. This was used for the first psophometers, in the 1930s.^[2] As the human-perceived level of noise is more important for telephony than their raw voltage, a modern psophometer incorporates a weighting network to represent this perception.^[1][2][3] The characteristics of the weighting network depend on the type of circuit under investigation, such as whether the circuit is used to normal speech standards (300 Hz – 3.3 kHz), or for high-fidelity broadcast-quality sound (50 Hz – 15 kHz).^[1]

The name was coined in the 1930s, on a basis from Ancient Greek: ψόφος, romanized: psóphos, lit. 'noise', itself derived from Ancient Greek: ψό, lit. 'an exclamation of disgust'.^[4] It is unrelated to Ancient Greek: σοφός, romanized: sóphos, lit. 'wisdom'.

The '-meter' suffix Ancient Greek: μέτρον, romanized: métron, lit. 'tool for measuring' was already widely used in English, but also derives originally from Greek.^[4]

• Psophometric voltage

•  This article incorporates public domain material from Federal Standard 1037C. General Services Administration. Archived from the original on 2022-01-22.