Originally Posted by
brakedwell
Did they have DB meters in thos days?
During the war, yes. In earlier times, according to an article by one H.H. Scott (the man known for early valve hifi design), attempts were made before standards were agreed upon - some devices used carbon mikes, others the best quality condenser microphones available. Some equipment setups came in the form of 4-5 wooden boxes that, in total, weighed in at over 100lbs, with batteries.
Much of the early research involved the quantification of human speech, thus the VU meter was born. This began to gather steam in the mid 1930s in the US, with industry standards coming in 1942, and international adoption in 1953. The dB meter scale was first used in the 1930s.
Noise regulation did not begin in the states until the early 1970s and specific commercial aircraft studies did not begin (understandably) until the screamin-mimi turbojet days of the 1960s - although such research was generally focused on external noise in and around airports and laws were not passed in the US until 1968.
General Radio Co. hand-held model from the early 1950s, a 4 valve unit with interchangeable microphones promised a +/-1dB accuracy on "average machine noises":
Fully transistorized "gun type" unit from LEA of France circa 1960:
A more commonly seen device from the very well known B&K of Denmark, also produced in the 1960s, took the shape used for decades afterwards and used a condenser microphone:
