Original sentence: Double-blind testing has been required in the approval of new medicines since about 1960
Edited sentence: ) should really be tested by "double-blind (D-B)" listening comparisons before they are offered for sale.After the test is completed, the notes are decoded.Attempted improvements in hardware (equipment like microphones, loudspeakers, etc.If this is not done, it is unfortunately too easy for the power of suggestion--similar to the placebo effect--to convince people that the new thing is audibly better.It is sometimes easy to convince yourself that a new thing sounds different, but a double-blind test prevents anyone from identifying which equipment is new versus old.Many new developments in this field are measurably better, for example the ability to reproduce frequencies above 20 kHz, but nobody can hear the difference, so they are not audibly better.That could be a single-blind test, but if even the person operating the switch does not know which is new or old, then it is double-blind.The D-B test involves hiding both the old and new equipment from view, and taking notes on which one the listener thinks sounds better, with all notes written in code.This kind of testing has been required in the approval of new medicines since about 1960