88The shift from coil-type microphones to condenser-type microphones(1-inch microphones)Covering the audible range(1/2-inch microphone)The NA-07 sound level meter released in 1964 was equipped with a coil-type 1-inch microphone. While the coil-type microphones were inexpensive, robust, and relatively resistant to vibration and humidity, they had low sensitivity and were not suitable for measurements in the high frequency bands. In response, we shifted to using condenser-type mi-crophones. The first product to use this microphone type was the NA-09 sound level meter, which was released in 1969.Masato MorikawaSound & Vibration Sensor R&D Group, R&D Department, R&D Center. He has contributed to the development of microphones, sound calibrators, and comparison couplers for sound and vibration measuring instruments. He is currently involved in the design and development of all types of calibrators.This product was developed to cover the audible range that can’t be measured with a 1-inch microphone using just a single sound level meter. By reducing the microphone diameter to 1/2 inch, we can expand the measurement frequency range to 20 kHz. This has since become the standard size for measuring microphones.Ayako SuzukiSound & Vibration Sensor R&D Group, R&D Department, R&D Center. Joined Rion in 2011. Since then, she has been involved in the development of microphones and preamplifiers. Her current work focuses on microphones for high-temperature environments.One of the six business plans set out in 1940 by the Kobayasi Institute of Physical Research, Rion’s parent company, was research on the piezoelectricity of Rochelle salt. Rochelle salt is the crystal of potassium sodium tartrate, known for its property of swiftly capturing sound waves. During World War II, Germany was quick to adopt this material to develop a sonar defense system. In 1944, Kobayasi Riken Co., Ltd. (the predecessor of Rion) was established to commercialize the research results of the Kobayashi Institute of Physical Research, and its research efforts were focused on the development of piezoelectric oscillators (crystal oscillators) using Rochelle salt crystals. The first microphone developed in 1946 was the M-101. The M-201, which was developed later, was recognized for its high moisture-proof performance, and Rion received orders from NEC on behalf of the occupying forces. This was the beginning of the measuring microphones that currently serve as one of the pillars of the Rion product lineup.A microphone is a tool for converting sound into an electrical signal. The applications of Rion microphones can be broadly divided into two categories. The first is environmental noise measurement, for which the microphone is attached to the tip of a sound level meter. The second is research and development of industrial products.The initial microphones were the coil-type microphones, which use permanent magnets to detect sound with magnetic force. But this method had low sensitivity and difficulty in picking up high-pitched (high frequency) sounds. From around 1967, condenser-type microphones, which detect sound by measuring the change in capacitance between a pair of opposing electrodes, came into use. They were placed inside the NA-51 precision sound level meters and NA-09 sound level meters. Even today, coil-type microphones are still commonly used for music applications, including karaoke equipment. But the ones generally used for measurement applications are condenser-type microphones.The development began with microphones with a diameter of one inch, or 25.4 mm. The size of a microphone is generally expressed by the diameter of the tip. While the audible range, or the range of sounds perceptible to humans, is between 20 Hz and 20 kHz, the one-inch microphone can only measure up to around 10 kHz due to structural reasons. That wasn’t sufficient for a component of a sound level meter. Then the 1/2-inch microphone, half the diameter of the initial model, was developed to cover the entire human audible range with a single sound level meter unit. As it can pick up high-frequency sounds up to 20 kHz, this has become the standard size and is currently used in all of Rion’s sound level meters.The next microphone to appear was the 1/4-inch microphone. This could pick up frequencies beyond those audible to the human ear and made it possible to measure into the ultrasonic range of 100 kHz.As described above, microphones have evolved to become smaller. However, smaller microphones don't necessarily mean better performance. While 1-inch microphones aren’t ideal for picking up high-frequency sounds, they excel at low-frequency sounds. And since the sensitivity of sound detection is proportional to the area of the diaphragm, 1-inch microphones can measure The history of microphone development goes back to our company’s founding days.NA-07 sound level meterNA-09 sound level meterUC-53
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