From the HB1E microphone, the brainchild of the great Alan Blumlein, to the American RCA 44-BX, perhaps the single most recognisable ribbon microphone, we're extremely proud of our vast and historic collection of microphones.

The custodian of these 500+ microphones since the early '70s has been legendary Technical Engineer Lester Smith, who takes meticulous care and attention of each one. A unique method to Abbey Road in which he achieves this is through the RS144 Acoustical Noise Generator.

The Acoustical Noise Generator, more commonly known as a noise gun, is a standard means of measurement to help check the sensitivity of a microphone at the studio. There are only three in existence, designed especially for use within Abbey Road Studios. Take a look below at the noise gun's manual written by former Chief Technical Engineer, Mike Batchelor.

Lester Smith explains the process of how he uses a noise gun on every Abbey Road microphone: "The machine produces white noise from the loudspeaker in front. Keeping a set distance of ten inches away from the centre diaphragm of the microphone, there is a phonometer which then measures the output sound. When it's set, a reading is received on the external meter of how many millivolts is produced which allows me to know if the levels are correct or not."

These are then documented in Lester's vast records that he began in 1972 when he took on the role as microphone custodian. A detailed sketch of each microphone is followed by its reading, serial number and additional notes.