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ASME Y10.11-1984 — Letter Symbols and Abbreviations for Quantities Used in Acoustics
🎧 ANSI/ASME Y10.11-1984 is an American National Standard published by The American Society of Mechanical Engineers, superseding the 1953 edition (ASA Y10.11-1953, R1959) of Letter Symbols for Acoustics. This revision introduced two notable changes: for the first time standard abbreviations are included alongside letter symbols for quantities used in acoustics, and the Standard now covers many quantities used in other fields as well, being in essential agreement with the American National Standard Letter Symbols for Quantities Used in Electrical Science and Electrical Engineering. Letter symbols for sound power and sound power level were chosen in collaboration with Accredited Standards Committee S1 on Acoustics. The Standard was approved by the Y10 Standards Committee and approved as an American National Standard by ANSI on May 17, 1984.
💡 Two key concepts: a letter symbol is a single-letter identification of a physical quantity and is independent of language; an abbreviation is a letter combination that represents a word or name in a particular language (e.g., SPL in English). They differ in nature and must not be confused.
1. Scope and General Framework 📌
Y10.11-1984 includes: Section 1 Scope, Section 2 Purpose, Section 3 References, Section 4 Definitions, and Section 5 Rules for Correct Usage, followed by a large set of tables (Table 1 through Table 12) forming the symbol and abbreviation lists. The table structure is as follows:
- Tables 1–5: basic-field symbols — space and time, mechanics, heat, radiation and light, electricity and magnetism;
- Table 6: Acoustics — the core of the Standard;
- Table 7: Electroacoustics;
- Table 8: Underwater Sound;
- Table 9: Levels and Noise Ratings;
- Table 10: Psychoacoustics;
- Tables 11 and 12: alphabetical lists of quantity symbols and of abbreviations.
This organization — from fundamentals to specialties, from quantities to units to abbreviations — makes the Standard directly usable in acoustics monographs, journal papers, product documentation, and standardized test methods.
⚠️ Note: the Standard states that no addenda or written interpretations of the requirements of this edition will be issued. Users must rely on the text of this edition itself and the referenced ISO/IEC documents; unofficial annotations are not authoritative.
2. Rules for Correct Usage and Typography ✍️
Section 5, “Rules for Correct Usage,” is the heart of the document, refining the general principles of the Y10 series into operational rules:
- Quantity symbols in italic: symbols for physical quantities (e.g., sound pressure p, frequency f) are printed in italic; unit symbols (e.g., Hz, Pa, dB) are printed in roman (upright) type;
- Subscripts and superscripts: subscripts distinguish states, frequencies, or reference values (e.g., prms for root-mean-square sound pressure); superscripts denote powers, labels, or units;
- Vectors in bold italic: vector quantities are printed in boldface italic, and their magnitudes in ordinary italic;
- Language independence: a symbol is independent of language — for electromotive force the symbol is E, while the abbreviation is emf in English, fem in French, and EMK in German, yet the symbol E is the same worldwide.
These rules give acoustics papers, test reports, and national standards a common “language,” eliminating ambiguity caused by language-dependent abbreviations.
3. Table of Acoustics Quantity Symbols 🧮
The table below excerpts the most frequently used acoustics quantity symbols from the Standard, with their SI units:
| Quantity | Symbol | Unit | Remarks |
|---|---|---|---|
| Sound pressure | p | Pa | Instantaneous pressure minus static pressure |
| Frequency | f | Hz | Number of vibration cycles per second |
| Wavelength | λ | m | Distance between adjacent points of equal phase |
| Speed of sound | c | m/s | Propagation speed of sound in a medium |
| Sound intensity | I | W/m² | Sound power passing through unit area |
| Sound power | P or W | W | Total acoustic energy radiated per second |
| Acoustic impedance | Za | Pa·s/m³ | Ratio of sound pressure to volume velocity |
| Sound pressure level | Lp | dB | Lp = 20 lg(p/pref), pref = 20 μPa |
| Sound power level | LW | dB | LW = 10 lg(W/Wref), Wref = 1 pW |
| Loudness level | LN | phon | Subjective psychoacoustic measure of loudness |
The Standard further defines symbols in electroacoustics (transducer sensitivity, directivity, efficiency), in underwater sound (sonar equation quantities such as propagation loss, target strength, and reverberation level), in levels and noise ratings (equivalent continuous level Leq, day-night level Ldn), and in psychoacoustics (loudness, pitch, masking). These provisions directly support the implementation of noise-testing standards such as ISO 1996 and ISO 3744.
💡 The 20 vs. 10 factor in level formulas: sound pressure level uses 20 lg because sound pressure is a field quantity (squared to become proportional to power), while sound power level uses 10 lg because sound power is already a power quantity. Confusing the two introduces a 10 or 20 dB error — always verify the formula.
4. Engineering Practice Essentials 🛠️
- 🎯 Noise test reports: label measurement-point sound pressure levels Lp, A-weighted levels LA, and sound power levels LW per the Y10.11 symbol system, and state reference values and weighting networks to keep data comparable.
- 🔬 Electroacoustic product development: use the standard symbols for transducer sensitivity, frequency response, and impedance curves to interface smoothly with international standards such as IEC 60268.
- 🌊 Underwater acoustics: write sonar-equation quantities (transmission loss TL, target strength TS, reverberation level RL) per Table 8 to reduce the risk of mixing military and civil conventions.
- 📄 Academic papers: provide a symbol table at the front of a paper and state “symbols per ANSI/ASME Y10.11-1984” to speed up review and reader communication.
🚨 Common mistake: treating unit symbols as quantity symbols — writing “dB” for the sound pressure level itself, or “Hz” for the quantity frequency. The correct style is f = 1000 Hz and Lp = 85 dB — quantity symbols in italic, unit symbols in roman, both required.
5. Frequently Asked Questions ❓
❓ Q: How do Y10.11-1984 acoustics symbols relate to ISO standards?
A: The Standard chose the symbols for sound power and sound power level in collaboration with Standards Committee S1, and is in essential agreement with the electrical letter-symbol standard; its system is broadly compatible with ISO 80000-8 (Acoustics), though a few symbol differences should be checked against the referenced documents.
A: The Standard chose the symbols for sound power and sound power level in collaboration with Standards Committee S1, and is in essential agreement with the electrical letter-symbol standard; its system is broadly compatible with ISO 80000-8 (Acoustics), though a few symbol differences should be checked against the referenced documents.
❓ Q: What is the difference between Lp and LW?
A: Lp is the logarithmic ratio of the sound pressure at a point to a reference pressure — it varies with distance and position. LW is the logarithmic ratio of the total radiated power of a source to a reference power — it is position-independent. Sound power level is used for product noise rating; sound pressure level is used for environmental noise assessment.
A: Lp is the logarithmic ratio of the sound pressure at a point to a reference pressure — it varies with distance and position. LW is the logarithmic ratio of the total radiated power of a source to a reference power — it is position-independent. Sound power level is used for product noise rating; sound pressure level is used for environmental noise assessment.
❓ Q: Why must abbreviations be distinguished from symbols?
A: Abbreviations depend on language (emf/fem/EMK), whereas symbols do not. Because acoustics involves international collaboration and multilingual documents, keeping symbols language-independent prevents confusion among language-specific abbreviations.
A: Abbreviations depend on language (emf/fem/EMK), whereas symbols do not. Because acoustics involves international collaboration and multilingual documents, keeping symbols language-independent prevents confusion among language-specific abbreviations.
❓ Q: Does the Standard issue written interpretations?
A: This edition explicitly states that no addenda or written interpretations will be issued. In case of ambiguity, follow the text of the Standard and the referenced ISO/IEC documents.
A: This edition explicitly states that no addenda or written interpretations will be issued. In case of ambiguity, follow the text of the Standard and the referenced ISO/IEC documents.
