Richard Clark wrote:
"It just occiurred to me that my mock response of 43 is as good as
any-....."

Almost, but the subject does have reference points though "threshold of
hearing" has almost as many values as there are people, or maybe more
than the population, depending on conditions.

Keith Henney in his 1938 "Principles of Radio" says:
"Loudspeakers in general are notoriously inefficient - the best in
common use is not over 30 per cent. Most of them are less than 5%
efficient."

In the years since 1938, efficiency has not made a big improvement.
Headphones are likewise inefficient and vary widely from sample to
sample.

Harold Ennes says in "Broadcast Maintenance":
"A level of 0.0002 dyne per square centimeter is considered to be the
threshold of audibility."

According to Fig 1-4 in the Ennes book, this is an intensity of 0 db. A
sound pressure of 0.00002 dynes per square centimeter is a sound
intensity of -20 dB, while 0.002 dynes per square centimeter is +20 dB.

Broadcast microphones are said to produce a power output of from -50 to
-65 dBm at a sound pressure of 10 dynes per square centimeter.

Sound transducers are said to vary by 15 dB in sensitivity among those
of the best quality, and that is at a particular reference frequency and
without variations which depend on the location of the source with
respect to the microphone above. Then think of a comparison of
individual response curves of sound transducers. It`s somewhat chaotic.

A description of headphone performance can be made which can be useful
to compare performance despite all of the problems. Microphones and
headsets of WW-2 are charted in "Electrical Communication Systems
Engineering" published by the War Department in April 1945. Useful
characterizations can also be made of other sound transducers.

Best regards, Richard Harrison, KB5WZI