434:. Even today, the best speakers are likely to generate around 1 to 3% of total harmonic distortion, corresponding to 30 to 40 dB below fundamental. This is not good enough, given the steep rise in loudness (rising to as much as 24 dB per octave) with frequency revealed by the equal-loudness curves below about 100 Hz. A good experimenter must ensure that trial subjects really hear the fundamental and not harmonics—especially the third harmonic, which is especially strong as a speaker cone's travel becomes limited as its suspension reaches the limit of compliance. A possible way around the problem is to use acoustic filtering, such as by resonant cavity, in the speaker setup. A flat free-field high-frequency response up to 20 kHz, on the other hand, is comparatively easy to achieve with modern speakers on-axis. These effects must be considered when comparing results of various attempts to measure equal-loudness contours.
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resonances. Headphone testing is, therefore, a good way to derive equal-loudness contours below about 500 Hz, though reservations have been expressed about the validity of headphone measurements when determining the actual threshold of hearing, based on the observation that closing off the ear canal produces increased sensitivity to the sound of blood flow within the ear, which the brain appears to mask in normal listening conditions. At high frequencies, headphone measurement becomes unreliable, and the various resonances of pinnae (outer ears) and ear canals are severely affected by proximity to the headphone cavity.
166:(1933). In their study, test subjects listened to pure tones at various frequencies and over 10 dB increments in stimulus intensity. For each frequency and intensity, the listener also listened to a reference tone at 1000 Hz. Fletcher and Munson adjusted the reference tone until the listener perceived that it had the same loudness as the test tone. Loudness, being a psychological quantity, is difficult to measure, so Fletcher and Munson averaged their results over many test subjects to derive reasonable averages. The lowest equal-loudness contour represents the quietest audible tone—the
454:. The high-frequency bands are wider in absolute terms than the low-frequency bands, and therefore "collect" proportionately more power from a noise source. However, when more than one critical band is stimulated, the signals to the brain add the various bands to produce the impressions of loudness. For these reasons equal-loudness curves derived using noise bands show an upwards tilt above 1 kHz and a downward tilt below 1 kHz when compared to the curves derived using pure tones.
33:
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97:, that boosts low and high-frequency components of the sound. These are intended to offset the apparent loudness fall-off at those frequencies, especially at lower volume levels. Boosting these frequencies produces a flatter equal-loudness contour that appears to be louder even at low volume, preventing the perceived sound from being dominated by the mid-frequencies where the ear is most sensitive.
201:(ISO) to revise the standard curves in ISO 226. They did this in response to recommendations in a study coordinated by the Research Institute of Electrical Communication, Tohoku University, Japan. The study produced new curves by combining the results of several studies—by researchers in Japan, Germany, Denmark, UK, and the US. (Japan was the greatest contributor with about 40% of the data.)
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450:—is said to have been based on the 40-phon Fletcher–Munson curve. However, research in the 1960s demonstrated that determinations of equal-loudness made using pure tones are not directly relevant to our perception of noise. This is because the cochlea in our inner ear analyzes sounds in terms of spectral content, each "hair-cell" responding to a narrow band of frequencies known as a
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This has resulted in the recent acceptance of a new set of curves standardized as ISO 226:2003. The report comments on the surprisingly large differences, and the fact that the original
Fletcher–Munson contours are in better agreement with recent results than the Robinson–Dadson, which appear to
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conducted listening trials in an attempt to find the best weighting curve and rectifier combination for use when measuring noise in broadcast equipment, examining the various new weighting curves in the context of noise rather than tones, confirming that they were much more valid than A-weighting
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Good headphones, well sealed to the ear, provide a flat low-frequency pressure response to the ear canal, with low distortion even at high intensities. At low frequencies, the ear is purely pressure-sensitive, and the cavity formed between headphones and ear is too small to introduce modifying
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to account for our reduced sensitivity to short bursts and clicks. It is widely used by
Broadcasters and audio professionals when they measure noise on broadcast paths and audio equipment, so they can subjectively compare equipment types with different noise spectra and characteristics.
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Real-life sounds from a reasonably distant source arrive as planar wavefronts. If the source of sound is directly in front of the listener, then both ears receive equal intensity, but at frequencies above about 1 kHz the sound that enters the ear canal is partially reduced by the
322:(outer ear). Off-centre sounds result in increased head masking at one ear, and subtle changes in the effect of the pinna, especially at the other ear. This combined effect of head-masking and pinna reflection is quantified in a set of curves in three-dimensional space referred to as
63:
and is arrived at by reference to equal-loudness contours. By definition, two sine waves of differing frequencies are said to have equal-loudness level measured in phons if they are perceived as equally loud by the average young person without significant hearing impairment.
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produced a new experimental determination that they believed was more accurate. It became the basis for a standard (ISO 226) that was considered definitive until 2003, when ISO revised the standard on the basis of recent assessments by research groups worldwide.
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and a variety of other sounds that, because of their brief impulsive nature, do not give the ear and brain sufficient time to respond. The results were reported in BBC Research Report EL-17 1968/8 entitled
208:
According to the ISO report, the
Robinson–Dadson results were the odd one out, differing more from the current standard than did the Fletcher–Munson curves. The report states that it is fortunate that the
469:, which differed from the A-weighting curve, showing more of a peak around 6 kHz. These gave a more meaningful subjective measure of noise on audio equipment, especially on the newly invented
340:, and for a long time the difference from the Fletcher–Munson curves was explained partly on the basis that the latter used headphones. However, the ISO report actually lists the latter as using
326:(HRTFs). Frontal presentation is now regarded as preferable when deriving equal-loudness contours, and the latest ISO standard is specifically based on frontal and central presentation.
112:
The first research on the topic of how the ear hears different frequencies at different levels was conducted by
Fletcher and Munson in 1933. Until recently, it was common to see the term
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used to refer to equal-loudness contours generally, even though a re-determination was carried out by
Robinson and Dadson in 1956, which became the basis for an ISO 226 standard.
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Churcher and King carried out a second determination in 1937, but their results and
Fletcher and Munson's showed considerable discrepancies over parts of the auditory diagram.
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that is free from reflections down to 20 Hz. Until recently, it was not possible to achieve high levels at frequencies down to 20 Hz without high levels of
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Because no HRTF is involved in normal headphone listening, equal-loudness curves derived using headphones are valid only for the special case of what is called
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is now preferred, of which the
Fletcher–Munson curves are now a sub-set, and especially since a 2003 survey by ISO redefined the curves in a new standard.
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With speakers, the opposite is true. A flat low-frequency response is hard to obtain—except in free space high above ground, or in a very large and
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when attempting to measure the subjective loudness of noise. This work also investigated the response of human hearing to tone-bursts, clicks,
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The report also comments on the large differences apparent in the low-frequency region, which remain unexplained. Possible explanations are:
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Subjects were not properly rested for days in advance, or were exposed to loud noise in traveling to the tests, which tensed the
79:. Fletcher–Munson curves have been superseded and incorporated into newer standards. The definitive curves are those defined in
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and Wilden A. Munson, and reported in a 1933 paper entitled "Loudness, its definition, measurement and calculation" in the
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to a maximum of around 20,000 Hz, although the upper hearing limit decreases with age. Within this range, the
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are one of many sets of equal-loudness contours for the human ear, determined experimentally by
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when presented with pure steady tones. The unit of measurement for loudness levels is the
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Fletcher, H. and Munson, W. A. "Loudness, its definition, measurement and calculation",
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Full
Revision of International Standards for Equal-Loudness Level Contours (ISO 226)
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The criteria used for judging equal loudness at different frequencies had differed.
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standard was based turns out to have been in agreement with modern determinations.
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773:"Precise and Full-range Determination of Two-dimensional Equal Loudness Contours"
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Precise and Full-range
Determination of Two-dimensional Equal Loudness Contours
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headphones, though it doesn't make clear how
Robinson–Dadson achieved
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Test your hearing – A tool for measuring your equal-loudness contours
696:"Fletcher Munson Curve: The Equal Loudness Contour of Human Hearing"
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recommendation 468, but later adopted by numerous standards bodies (
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753:"A re-determination of the equal-loudness relations for pure tones"
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A Model of Loudness Applicable to Time-Varying Sounds AESJ Article
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Recent revision aimed at more precise determination – ISO 226:2023
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Fletcher and Munson first measured equal-loudness contours using
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811:"A measurement of equal-loudness level contours for tone burst"
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auditory system is sensitive to frequencies from about 20
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834:, 2nd Ed., 1999, edited Michael Talbot Smith, Focal Press.
27:
Frequency characteristics of hearing and perceived volume
520:) was based on the research, and incorporates a special
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were derived in the 1960s, in particular as part of the
93:
often feature a "loudness" button, known technically as
882:
Evaluation of Loudness-level weightings and LLSEL JASA
809:
Ken’ichiro Masaoka, Kazuho Ono, and Setsu Komiyama,
55:
spectrum, for which a listener perceives a constant
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2002:
951:
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The Assessment of Noise in Audio Frequency Circuits
318:, and also highly dependent on reflection off the
623:The Journal of the Acoustical Society of America
798:IEEE Transactions on Audio and Electroacoustics
438:Relevance to sound level and noise measurements
224:The equipment used was not properly calibrated.
619:"Equal-loudness-level contours for pure tones"
238:controlling low-frequency mechanical coupling.
199:International Organization for Standardization
85:International Organization for Standardization
3236:
907:
877:Equal-loudness contour measurements in detail
8:
862:Fletcher–Munson is not Robinson–Dadson (PDF)
838:An Introduction to the Psychology of Hearing
683:Journal of the Acoustical Society of America
77:Journal of the Acoustical Society of America
39:equal-loudness contours with frequency in Hz
390:. Unsourced material may be challenged and
281:. Unsourced material may be challenged and
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617:Suzuki, YĂ´iti; Takeshima, Hisashi (2004).
840:5th ed, Brian C.J. Moore, Elsevier Press.
721:
719:
717:
642:
410:Learn how and when to remove this message
301:Learn how and when to remove this message
609:
336:The Robinson–Dadson determination used
333:, which is not how we normally hear.
147:, largely due to the resonance of the
352:Headphones versus loudspeaker testing
7:
794:"Researches in loudness measurement"
388:adding citations to reliable sources
279:adding citations to reliable sources
800:, Vol. 14:3 (Sep 1966), pp.141–151.
213:Fletcher–Munson curve on which the
143:is most sensitive between 2 and 5
25:
817:, Vol. 22 (2001), No. 1 pp.35–39.
815:Acoustical Science and Technology
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251:
243:Side versus frontal presentation
832:Audio Engineer's Reference Book
324:head-related transfer functions
551:CCIR (ITU) 468 Noise Weighting
500:curve, originally proposed in
1:
172:. The highest contour is the
169:absolute threshold of hearing
573:, the same concept in vision
446:curve—in widespread use for
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127:Experimental determination
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762:(1956), pp. 166–181.
561:ITU-R 468 noise weighting
541:Audio quality measurement
498:ITU-R 468 noise weighting
467:audio quality measurement
3268:Architectural acoustics
792:Bauer, B., Torick, E.,
751:D. W. Robinson et al.,
121:equal-loudness contours
18:Equal-loudness contours
3355:Fletcher–Munson curves
3350:Equal-loudness contour
3260:Acoustical engineering
771:YĂ´iti Suzuki, et al.,
587:Robinson–Dadson curves
109:
101:Fletcher–Munson curves
69:Fletcher–Munson curves
45:equal-loudness contour
40:
3491:Hermann von Helmholtz
3389:Fundamental frequency
3293:Sympathetic resonance
741:on September 27, 2007
108:
95:loudness compensation
35:
582:Pure tone audiometry
473:tape recorders with
384:improve this section
275:improve this section
49:sound pressure level
3511:Werner Meyer-Eppler
3421:Missing fundamental
635:2004ASAJ..116..918S
571:Luminosity function
522:quasi-peak detector
432:harmonic distortion
186:Robinson and Dadson
159:of the middle ear.
3394:Frequency spectrum
927:by standard number
779:2007-09-27 at the
757:Br. J. Appl. Phys.
702:. 16 November 2017
465:4550 standard for
110:
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3623:Audio engineering
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3567:Musical acoustics
3399:harmonic spectrum
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941:ISO romanizations
685:5, 82–108 (1933).
644:10.1121/1.1763601
592:Sound level meter
448:noise measurement
420:
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331:side-presentation
311:
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236:stapedius muscles
175:threshold of pain
153:transfer function
119:The generic term
16:(Redirected from
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3496:Carleen Hutchins
3428:Combination tone
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597:Weighting filter
566:Listener fatigue
471:compact cassette
459:weighting curves
428:anechoic chamber
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47:is a measure of
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3618:Psychoacoustics
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3367:Audio frequency
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3139:
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2209:
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2159:
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2109:
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1991:
1986:
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3283:Soundproofing
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3278:Reverberation
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452:critical band
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369:This section
367:
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291:December 2020
284:
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260:This section
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50:
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38:
34:
30:
19:
3531:Thomas Young
3481:Jens Blauert
3469:Acousticians
3349:
3063:27000 series
1095:
852:ISO Standard
837:
831:
814:
805:
797:
788:
767:
759:
756:
747:
736:the original
728:ISO 226:2003
727:
706:November 17,
704:. Retrieved
699:
690:
682:
677:
626:
622:
612:
495:
490:
481:BBC Research
479:
456:
441:
425:
421:
406:
400:October 2015
397:
382:Please help
370:
346:compensation
345:
341:
338:loudspeakers
335:
330:
328:
312:
297:
288:
273:Please help
261:
219:
207:
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196:
183:
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167:
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130:
120:
118:
113:
111:
89:
80:
76:
68:
66:
44:
42:
29:
3501:Franz Melde
3476:John Backus
3460:Subharmonic
3313:Spectrogram
2851:20000–29999
2003:10000–19999
700:Ledger Note
536:A-weighting
444:A-weighting
342:compensated
316:head shadow
215:A-weighting
51:, over the
3612:Categories
3562:Ultrasound
3552:Infrasound
3338:Bark scale
2630:16949 (TS)
2227:11941 (TR)
925:standards
825:References
486:pink noise
164:headphones
91:Amplifiers
3638:Acoustics
3443:Resonance
3343:Mel scale
3273:Monochord
3252:Acoustics
2585:15926 WIP
1949:9592/9593
1874:9000/9001
1762:8805/8806
653:0001-4966
577:Mel scale
546:Audiogram
371:does not
262:does not
149:ear canal
141:human ear
83:from the
53:frequency
3597:Category
3438:Overtone
3406:Harmonic
3210:Category
935:List of
777:Archived
669:15865914
661:15376658
529:See also
457:Various
184:In 1956
157:ossicles
151:and the
57:loudness
3384:Formant
3111:29199-2
2983:23094-2
2978:23094-1
2968:23090-3
2837:19794-5
2832:19775-1
2620:16612-2
2610:16355-1
2299:13406-2
2257:12234-2
2025:10118-3
631:Bibcode
392:removed
377:sources
283:removed
268:sources
155:of the
81:ISO 226
3577:Violin
3411:Series
3125:30000+
1964:9797-1
1772:8820-5
1717:8501-1
1273:1073-2
1268:1073-1
952:1–9999
667:
659:
651:
3633:Sound
3572:Piano
3557:Sound
3371:pitch
3333:Pitch
3192:80000
3187:56000
3182:55000
3177:50001
3172:45001
3167:42010
3162:40500
3157:39075
3152:38500
3147:37001
3142:32000
3137:31000
3132:30170
3116:29500
3106:29148
3102:29110
3098:28000
3093:27729
3088:27006
3083:27005
3078:27002
3073:27001
3068:27000
3058:26324
3053:26300
3048:26262
3043:26000
3038:25964
3033:25178
3028:24728
3023:24707
3018:24617
3013:24613
3008:24517
3003:23941
2998:23360
2993:23271
2988:23270
2973:23092
2963:23009
2958:23008
2953:23003
2948:23000
2943:22537
2938:22395
2933:22301
2928:22300
2923:22275
2918:22000
2913:21827
2908:21500
2903:21122
2898:21047
2893:21001
2888:21000
2883:20830
2878:20802
2873:20400
2868:20121
2863:20022
2858:20000
2842:19831
2827:19770
2822:19757
2817:19752
2812:19600
2807:19510
2802:19509
2797:19508
2792:19507
2787:19506
2782:19505
2777:19503
2772:19502
2767:19501
2762:19500
2757:19439
2752:19407
2747:19136
2742:19125
2737:19115
2732:19114
2715:19092
2710:19011
2705:19005
2700:18916
2695:18629
2690:18245
2685:18181
2680:18014
2675:18004
2670:17799
2665:17506
2660:17442
2655:17369
2650:17203
2645:17100
2640:17025
2635:17024
2625:16750
2615:16485
2605:16262
2600:16023
2595:15938
2590:15930
2580:15926
2575:15924
2570:15919
2565:15897
2560:15707
2548:15706
2543:15693
2538:15686
2533:15511
2528:15504
2523:15438
2518:15445
2501:15444
2496:15408
2491:15398
2486:15291
2481:15288
2476:15189
2471:15022
2466:14971
2461:14882
2456:14764
2451:14698
2446:14651
2441:14649
2436:14644
2431:14617
2379:14496
2374:14443
2369:14396
2364:14289
2359:14224
2354:14031
2349:14000
2344:13818
2339:13816
2334:13616
2329:13584
2324:13568
2319:13567
2314:13490
2309:13485
2304:13450
2294:13399
2289:13250
2284:13216
2267:13211
2262:12620
2252:12207
2247:12182
2242:12052
2237:12006
2232:11992
2222:11941
2212:11940
2207:11898
2202:11889
2197:11801
2192:11785
2187:11784
2182:11783
2177:11544
2172:11404
2167:11179
2162:11172
2157:11170
2152:11073
2147:10967
2142:10962
2137:10957
2132:10861
2127:10746
2122:10664
2117:10646
2112:10628
2107:10589
2102:10585
2097:10383
2065:10303
2060:10279
2055:10218
2050:10206
2045:10179
2040:10165
2035:10161
2030:10160
2020:10116
2015:10007
2010:10006
739:(PDF)
732:(PDF)
665:S2CID
604:Notes
556:dB(A)
475:Dolby
320:pinna
133:human
3547:Echo
3453:Node
3379:Beat
3369:and
2090:-238
1994:9995
1989:9985
1984:9984
1979:9945
1974:9899
1969:9897
1959:9660
1954:9594
1944:9564
1939:9529
1934:9506
1929:9496
1924:9407
1919:9362
1914:9314
1909:9293
1904:9241
1899:9227
1894:9141
1889:9126
1884:9075
1879:9036
1869:8879
1822:-8-I
1777:8859
1767:8807
1757:8691
1752:8652
1747:8651
1742:8632
1737:8613
1732:8601
1727:8583
1722:8571
1712:8373
1707:8217
1702:8178
1697:8093
1692:8000
1687:7942
1682:7816
1677:7813
1672:7812
1667:7811
1662:7810
1657:7736
1652:7637
1640:7498
1635:7200
1630:7185
1625:7098
1620:7064
1615:7027
1610:7010
1605:7002
1600:7001
1595:6943
1590:6709
1585:6523
1580:6438
1575:6429
1570:6425
1565:6385
1560:6373
1555:6346
1550:6344
1545:6166
1540:5964
1535:5807
1530:5800
1525:5776
1520:5775
1515:5725
1510:5428
1505:5427
1500:5426
1495:5218
1490:4909
1485:4217
1480:4165
1475:4157
1470:4031
1465:3977
1460:3950
1455:3901
1450:3864
1445:3602
1440:3601
1435:3307
1430:3297
1408:3166
1403:3103
1398:3029
1393:2921
1388:2852
1383:2848
1378:2788
1373:2720
1368:2711
1363:2709
1358:2533
1353:2281
1348:2240
1343:2146
1338:2145
1333:2108
1328:2047
1323:2033
1318:2022
1313:2015
1308:2014
1303:1989
1298:1745
1293:1629
1288:1538
1283:1413
1278:1155
1263:1007
1258:1004
1253:1000
1076:68-1
708:2017
657:PMID
649:ISSN
502:CCIR
496:The
442:The
375:any
373:cite
266:any
264:cite
234:and
211:phon
131:The
67:The
61:phon
2424:-20
2419:-17
2414:-14
2409:-12
2404:-11
2399:-10
2085:-28
2080:-22
2075:-21
2070:-11
1862:-16
1857:-15
1852:-14
1847:-13
1842:-12
1837:-11
1832:-10
1248:999
1243:965
1238:898
1233:860
1228:843
1223:838
1218:764
1213:732
1208:704
1203:690
1198:668
1193:657
1188:646
1156:639
1151:519
1146:518
1141:500
1136:361
1131:306
1126:302
1121:262
1116:261
1111:259
1106:233
1101:228
1096:226
1091:217
1086:216
1081:128
1069:-13
1064:-12
1059:-11
1054:-10
923:ISO
639:doi
627:116
518:ITU
514:JIS
510:BSI
506:IEC
463:DIN
386:by
277:by
209:40-
145:kHz
43:An
37:ISO
3614::
2725:-2
2720:-1
2553:-2
2511:-9
2506:-3
2394:-6
2389:-3
2384:-2
2277:-2
2272:-1
2216:-2
1827:-9
1817:-8
1812:-7
1807:-6
1802:-5
1797:-4
1792:-3
1787:-2
1782:-1
1645:-1
1423:-3
1418:-2
1413:-1
1181:-6
1176:-5
1171:-3
1166:-2
1161:-1
1049:-9
1044:-8
1039:-7
1034:-6
1029:-5
1024:-4
1019:-3
1014:-1
1009:-0
1004:31
999:17
994:16
943:–
939:–
813:,
796:,
775:.
755:,
716:^
698:.
663:.
655:.
647:.
637:.
625:.
621:.
516:,
512:,
508:,
493:.
348:.
178:.
137:Hz
3244:e
3237:t
3230:v
2218:)
2214:(
989:9
984:7
979:6
974:4
969:3
964:2
959:1
915:e
908:t
901:v
783:.
760:7
710:.
671:.
641::
633::
413:)
407:(
402:)
398:(
394:.
380:.
304:)
298:(
293:)
289:(
285:.
271:.
20:)
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