Industry pressure forced ISO to standardize A-weighted SPL before a better loudness-based method

Evidence

Pushed by industry, the International Standardization Organization (ISO) was forced to standardize a method that was not only practical but that would also indicate correct and adequate values. Standardization is a time-consuming process, and it was finally decided to solve the problem in two steps. The first step produced a simple method that could easily be implemented using relatively cheap equipment. The ISO was aware of the fact that this initial method, measurement of A-weighted SPL, might produce inaccurate or even misleading results in noise control. Therefore, the ISO produced a second standard that was not as simple as the former but produced much more appropriate values based on the human sensation of loudness. Two corresponding methods have been described as loudness calculation procedures in ISO 532 and were published only a few years after the dB (A)-proposal. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 1742

Categorization

• XREF: Connects to broader theme of measurement conventions being politically/industrially negotiated rather than purely scientific — parallels the reader’s work on how standards encode compromises.
• DEFINE: Clarifies the origin of dB(A) as a deliberately imperfect first-step standard versus the later, more psychophysically grounded ISO 532 loudness methods.