Factors that Influence Listeners Preferred Bass and Treble Balance in Headphones

Transcription

1 Factors that Influence Listeners Preferred Bass and Treble Balance in Headphones Dr. Sean E. Olive DIRECTOR ACOUSTIC RESEARCH Todd Welti SENIOR PRINCIPAL ACOUSTIC RESEARCHER Presented at the 139th Audio Engineering Society Convention, NYC, USA October 29-Nov

2 We ve been busy the past 2 years researching the perception and measurement of headphones Audio Engineering Society Convention Paper Presented at the 137th Convention 2014 October Los Angeles, CA, USA This convention paper has been reproduced from the author's advance manuscript, without editing, corrections, or consideration by the Review Board. The AES takes no responsibility for the contents. Additional papers may be obtained by sending request and remittance to Audio Engineering Society, 60 East 42 nd Street, New York, New York , USA; also see All rights reserved. Reproduction of this paper, or any portion thereof, is not permitted without direct permission from the Journal of the Audio Engineering Society. The Correlation Between Distortion Audibility and Listener Preference in Headphones Steve Temme 1, Sean E. Olive 2, Steve Tatarunis 3, Todd Welti 4, and Elisabeth McMullin 5 1,3 Listen, Inc., Boston, MA, 02118, USA stemme@listeninc.com, statarunis@listeninc.com Audio Engineering Society Convention Paper Presented at the 138th Convention 2015 May 7 10 Warsaw, Poland Improved Measurement of Leakage Effects for Circum-aural and Supra-aural Headphones Todd Welti Harman International Inc. Northridge CA, 91360, USA todd.welti@harman.com 9275 This paper was peer-reviewed as a complete manuscript for presentation at this Convention. This paper is available in the AES E-Library, All rights reserved. Reproduction of this paper, or any portion thereof, is not permitted without direct permission from the Journal of the Audio Engineering Society. Audio Engineering Society Convention Paper Presented at the 139th Convention 2015 October 29 November 1 New York, USA This paper was peer-reviewed as a complete manuscript for presentation at this Convention. This paper is available in the AES E-Library, All rights reserved. Reproduction of this paper, or any portion thereof, is not permitted without direct permission from the Journal of the Audio Engineering Society. Factors that Influence Listeners Preferred Bass and Treble Balance in Headphones Sean E. Olive 1 and Todd Welti 2 Harman International, Northridge, CA, 91329, USA 1 2 sean.olive@harman.com todd.welti@harman.com 2 ABSTRACT 2,4,5 Harman International Industries, USA sean.olive@harman.com, todd.welti@harman.com, Elisabeth.McMullin@harman.com It is well-known that the frequency response of loudspeakers and headphones has a dramatic impact on sound quality and listener preference, but what role does distortion have on perceived sound quality? To answer this question, five popular headphones with varying degrees of distortion were selected and equalized to the same frequency response. Trained listeners compared them subjectively using music as the test signal, and the distortion of each headphone was measured objectively using a well-known commercial audio test system. The correlation between subjective listener preference and objective distortion measurement is discussed. HARMAN International. Confidential. Copyright ABSTRACT Headphone leakage effects can have a profound effect on low frequency performance of headphones. A large survey, including over 2000 individual headphone measurements, was undertaken in order to compare leakage effects on human test subjects to leakage effects of the same headphones measured on a test fixture. Ten different commercially available headphones were used, each measured on eight different test subjects and a test fixture with several sets of pinnae. Modifications to the pinnae were investigated to see if the leakage effects measured on the test fixture could be made to better match the real word leakage effects measured on human test subjects. 1. INTRODUCTION Headphone leakage effects can have a profound effect on low frequency performance of headphones. Deviations of 20 db or more in the headphone response can easily result from varying amounts of leakage. The effect of a leak on a closed cavity is technically well understood [1]. Even so, for many headphone designs, Some previous related studies have been made comparing different pinna sets, such as in [2]. In this study different pinnae were considered, as well as different pinna hardness, but the focus was on reproducibility of measurements. There were no measurements made on human tests subjects for comparison to the artificial pinna. The current study includes a large number of ABSTRACT A listening experiment was conducted to study factors that influence listeners preferred bass and treble balance in headphone sound reproduction. Using a method of adjustment a total of 249 listeners adjusted the relative treble and bass levels of a headphone that was first equalized at the eardrum reference point (DRP) to match the in-room steady-state response of a reference loudspeaker in a reference listening room. Listeners repeated the adjustment five times using three stereo music programs. The listeners included males and females from different age groups, listening experiences, and nationalities. The results provide evidence that the preferred bass and treble balances in headphones was influenced by several factors including program, and the listeners age, gender and prior listening experience. The younger and less experienced listeners on average preferred more bass and treble in their headphones compared to the older, more experienced listeners. Female listeners on average preferred less bass and treble than their male counterparts. 1. INTRODUCTION Recent scientific investigations into alternative headphone target curves have found that listeners prefer them when compared to the standard diffuse and freefield headphone calibrations [1]-[4]. Olive et al. showed evidence that trained listeners preferred a headphone target response that closely matched the measured into whether the bass and treble levels of the headphone target response were optimized for best sound quality. To address this question, a follow up experiment was recently conducted wherein listeners directly adjusted the relative bass and treble levels of the headphone after it was equalized at the DRP to match the in-room

3 Research Motivation Current research indicates headphones calibrated to current standards (e.g. diffuse and free-field) are less preferred to new headphone calibrations Olive et al. (2014) developed a new headphone target curve based on an accurate loudspeaker in a reference listening room that was preferred to current standards and several highly-regarded headphones We tested it using 238 listeners in four different countries from different age groups, gender, trained vs untrained listeners HARMAN International. Confidential. Copyright

4 Previous Research (2014) Brand / Model Price Harman Target Curve Based on latest AES paper October Sennheiser HD800 $1500 Audeze LCD2 (rev 2) $995 Beats by Dre Studio Limited Edition $270 HARMAN International. Confidential. Copyright

5 Mean Preference Ratings (n=238 listeners)! 7 Preference Rating ! Harman Target Curve HP2 HP3 HP4 Headphone HARMAN International. Confidential. Copyright

6 Current Study Research Questions What are the preferred bass and treble level settings for a headphone equalized to simulate the in-room response of an accurate loudspeaker in a reference listening room? What is the influence of program, listeners age, listening experience, gender, culture on their preferred headphone spectral balance? HARMAN International. Confidential. Copyright

7 Method For Deriving Harman Target Curve Step 1: Choose an Revel Performa F208 loudspeaker accurate loudspeaker with flat on-axis, smooth off-axis response and directivity On-axis Listening Window First Reflections Predicted In-room Sound power Sound Power DI First Reflections DI HARMAN International. Confidential. Copyright

8 Method For Deriving Harman Target Curve Step 2: Using Harman Reference Listening Room standard stereo setup equalize speaker in reference listening room to produce flat in-room response at primary listening seat; response is based on spatial average of 9 mic positions HARMAN International. Confidential. Copyright

9 Equalizing the In-Room Loudspeaker Response to Flat left channel only Before EQ (Left Speaker) average left and right channels After EQ (Average of Left + Right Speaker) HARMAN International. Confidential. Copyright

10 Method For Deriving Harman Target Curve Step 3: At primary listening seat measure response at ear-drum using GRAS ear simulator mounted to head; take average based on 3 head positions \ +30 HARMAN International. Confidential. Copyright

11 Method for Deriving Harman Target Curve Step 4: Equalize headphone to match in-room response of loudspeaker measured at the ear drum. Determine what the optimal bass and treble balance should be through Method of Adjustment. HARMAN International. Confidential. Copyright

12 Listening Test Setup Custom ipad Test Software Sennheiser HD518 equalized to flat Harman Target Response Task: Using the two rotating knobs on the ipad adjust the bass and treble levels according to personal preference HARMAN International. Confidential. Copyright

13 Harman Headphone ipad Test Software Bass Control HARMAN International. Confidential. Copyright Treble Control 13

14 Listening Test Method Using a Method of Adjustment listeners adjust the bass and treble levels of the headphone in db db increments according to personal preference +5 db Repeat 5x using three -5 db programs Randomize starting level(s) and program order -10 db Figure 2 The frequency response of the bass and treble HARMAN International. Confidential. Copyright

15 Program Material Program / Artist / CD / Track / Label / Release Date Details ES / Estelle w. Kayne West / Shine/ American Boy / Atlantic Records, 2008, B00142Q7H8 / April SD / Steely Dan / Two Against Nature / Cousin Dupree / Giant Records /B00004GOXS/ February Hip Hop with male and female vocal Jazz Pop with Male Vocal JW / Jennifer Warnes/ Blue Raincoat /Bird on a Wire Rock Pop with Female Vocal HARMAN International. Confidential. Copyright

16 Long-term Spectrum of Programs HARMAN International. Confidential. Copyright

17 Listeners Group Country Sample Size (n) Gender Age of Listeners in Years Listening Experience % of Group % of Males % of Females Median SD None A Little Medium Harman NR USA 9 78% 22% A Lot Harman FH USA 24 83% 17% Harman KB Germany 72 93% 7% Harman SZ China 20 80% 20% Citrus College Loyola M. University (LMU) Harris College USA 24 75% 25% USA 15 93% 7% Canada 48 90% 10% JBL Dealers Varied % 0% TOTAL % 11% % 19% 32% 30% HARMAN International. Confidential. Copyright

18 HARMAN International. Confidential. Copyright RESULTS

19 Explanation of Listening Test Graphs 8 Preferred Bass and Treble Levels db Bass and Treble Filters Gain Relative Level (db) = Relative Level (db) db -2 Bass Treble Frequency (Hz) HARMAN International. Confidential. Copyright

20 Preferred Bass and Treble Levels Averaged across all programs and all listeners (n=249) 8 Relative Level (db) Bass Treble HARMAN International. Confidential. Copyright

21 Effect of Program on Preferred Bass and Treble Levels 8 Bass Treble 6 Relative Level (db) ES JW SD Program HARMAN International. Confidential. Copyright

22 Effect of Gender on Preferred Bass and Treble Levels Male Listeners (n=222) Female Listeners (n=27) 8 6 Relative Level (db) Bass Treble HARMAN International. Confidential. Copyright

23 Effect of Listening Experience on Preferred Bass and Treble Levels 8 Bass Treble 6 Relative Level (db) None Little Medium Amount A Lot Listening Experience HARMAN International. Confidential. Copyright

24 Effect of Age of Listener 8 Bass Treble 6 Relative Level (db) Listener s Age (years) HARMAN International. Confidential. Copyright

25 Listeners Country of Residence Canada Germany 21% 31% China 9% USA 40% HARMAN International. Confidential. Copyright

26 Country of Listener 8 Bass Treble 6 Relative Level (db) Canada China USA Germany Country of Listener HARMAN International. Confidential. Copyright

27 Listening Experience vs Country No Experience A little Medium A Lot of Experience Canada China USA Germany 8% 8% 10% 27% 14% 15% 33% 52% 31% 50% 35% 18% 25% 5% 40% 26% HARMAN International. Confidential. Copyright

28 Listening Groups 8 Bass Moderate Bass & Treble Lovers Treble Relative Level (db) Heavy Bass & Treble Lovers Harman NR Harman FH Harman KB Harman SZ Citrus College LMU Harris Insitute JBL Dealers Listening Group HARMAN International. Confidential. Copyright

29 Comparison With Previous Studies Bass Treble Relative Level (db) Olive & Welti (2015) Olive et al (2014) Olive et al (2014) Playback: Headphone Headphone Loudspeaker HARMAN International. Confidential. Copyright

30 Preferred Headphone Response as Measured at Ear Drum Reference Point Olive & Welti Headphone Target Curve (this study) Olive et al. Headphone Target Curve from [4] Loudspeaker equalized to flat in-room response [4] [4] S.E. Olive, T. Welti and E. McMullin, Listener Preferences for In-Room Loudspeaker and Headphone Target Responses, presented at the 135 th Convention, Audio Eng., Soc., preprint 8994, (2013 October). HARMAN International. Confidential. Copyright

31 Conclusions (1) Preferred levels averaged across all programs and listeners were: Bass = 6.6 db and Treble = -1.4 db Music Program a significant factor Listener Age is significant factor: younger (15-25 years) listeners tend to prefer high levels of bass (+1.6 db) and treble (+0.6 db) than older listeners (hearing loss could be a factor) Listening Experience a significant factor: Less experienced listeners prefer more bass and treble HARMAN International. Confidential. Copyright

32 Conclusions (2) Females preferred 1 db less bass and 2 db treble than male counterparts Germans on average preferred slightly less bass (< 1 db) than Chinese, Canadian, USA listeners (could be explained by higher mean age of German sample) HARMAN International. Confidential. Copyright

33 Some Limitations of Research Method of Adjustments in bass and treble not loudness compensated: some listeners may have simply boosted bass and treble because it made the music louder Listener sample was not randomly selected or balanced Listener training was self-reported (exception was Harman trained listeners) Programs limited to 3 samples Audiometric hearing performance was not tested (except Harman trained listeners) In practice, preferred bass and treble level may vary with background noise (masking) and headphone fit (leakage) HARMAN International. Confidential. Copyright

34 Take-aways The ideal headphone target curve is a moving target due to variations in: Program material ( circle of confusion / lack of meaningful standards in recording industry monitoring chain) Individual taste (age and experience seem to matter) Masking effects of background noise (bass/mids are masked) Variation in headphone fit (bass leakage) We need a simple bass / treble control on headphones to compensate for these variations HARMAN International. Confidential. Copyright

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36 Audio Engineering Society aes.org/conferences/2016/headphones/ 2016 AES International Conference on Headphone Technology August 24 th - 26 th, Aalborg, Denmark

37 Audio Engineering Society 2016 AES International Conference on Headphone Technology August 24 th - 26 th, Aalborg, Denmark Proposed Topics: Design Headphone Transducers: Technology, Measurement, Microdrivers, Smart - Control, Simulation Personalization Additional Sensors Wearing and Listening Comfort Applications Augmented Reality Mobile Spatial Audio Personal and Assistive Listening Binaural Techniques Up-Mixing Noise Control Monitoring and Analytic Listening Evaluation Headphone Quality Quality Standards Automatic Quality Evaluation Perceptual Audio Evaluation Perceptual Targets aes.org/conferences/2016/headphones/