National Standard for Acoustic Pressure

National Standard for Acoustic Pressure

One of the most fundamental and essential human senses is hearing. The realization of this physical quantity is an integral part of human life, connected to environmental protection and hearing safety by ensuring compliance with numerous legally mandated measuring instruments in this regulated field.

Primary Realization of Acoustic Pressure

Acoustics focuses on the realization of the unit of acoustic pressure at the primary level, which is conducted indirectly through the acoustic transfer impedance of an acoustically coupled microphone system. This is achieved by determining the sensitivity of standard measuring microphones (Mp in V/Pa) using the absolute primary reciprocity method in a pressure field within a small measurement chamber in an air environment.

The measure of acoustic pressure is the output voltage at the microphone terminals. The unit is maintained through the established sensitivity of the microphones.

Composition of the National Standard for Acoustic Pressure

The core assembly of the standard consists of an active measurement chamber, where two calibrated microphones are acoustically coupled. These microphones are connected via:

• Microphone preamplifiers
• Infrasound filters
• Digital voltmeters

In its active state, the measurement chamber is powered via an amplifier, receiving signals from a signal generator. The system also includes a control unit, which allows for the electrical switching of the microphone’s function between receiver and transmitter. The entire system is computer-controlled, utilizing electric and acoustic impedance parameters determined through other methods.

Unique Features of the National Standard

The standard setup employs a dual-microphone system placed within an active measurement chamber, integrated with specialized preamplifiers that provide nearly unitary gain. This unique system design is the only one of its kind in the world, achieving comparison measurement results at the reference frequency that are comparable to the world's best standards for this quantity.

Documents for download

• Osvedčenie (certifikát) (pdf, 413.2 kB)