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The Twentieth Annual Interactive Audio Conference
BBQ Group Report: Protecting Tomorrow’s Ears
Participants: A.K.A. "Deaf metal"

Michael Ricci, Akustica/Bosch Sensortec

Ty Kingsmore, Realtek Semiconductor Inc.
Vinny Nguyen, Apple Inc., Beats-ByDre Dafydd Roche, Texas Instruments Inc
Ilias Tsigkogiannis, Microsoft Corporation TVB Subrahmanyam, Analog Devices
Brad Lambert, Cirrus Logic Scott McNeese, Cirrus Logic
Matt Cowan, Audience/Knowles Trausti Thormundsson, Conexant
Leng Ooi, Google Dilli Sharma, Dolby Labs
Ajay Kanji, Tempo Semi Jann-Paul Huijser, NXP
Facilitator: Doug Peeler, Dell, Inc.  
  PDF download the PDF

Acknowledgment of Prior Work

The group brainstormed about the future headphones/ear buds but concluded that many technical specifications and product design recommendations have are already been covered by previous Bar-B-Q workgroups.  We thank everybody for their contribution in the past.

It was concluded that it is far more important to focus a solution for the hearing damage that is occurring today.

Problems addressed

  • Lack of active hearing protection in headsets
  • Sound quality variation
    • Hearing capability changes over lifespan
    • Variability in listener ears
  • Environmental contextual awareness, safety
  • Lack of globalized and harmonized standards.

Existing Situation

According to the World Health Origination study from Feb. 2015, 1.8 billion people are at high risk of getting hearing damage from recreational music listening of compressed digital files with ear-buds/headphones.




As audio professionals, we wish to add to the collection of medical and music industry work that has been conducted in recent decades.  Two facts are clear, people do not want to damage their hearing and they want to enjoy their music on the go.  As content creators, broadcasters, regulatory bodies and manufacturers of consumer audio product, we have not been able provide a comprehensive solution to protect peoples hearing while also improving the listening experience.

A combination of factors have combined into The-Perfect-Hearing-Damage-Storm.

  • The proliferation of smarts phones that are sold with inexpensive ear-buds designed for discretely making phone calls have become the primary means by which music is listened to. 
  • Music content creators (musicians, audio engineers, record labels, broadcasters) have been escalating “Volume Wars” vying for the loudest content to capture the listeners attention.  This started with FM broadcasts of CDs and to a large extent is still practiced with compressed Digital File formats such as AAC and MP3.   
  • Now the death-blow: .the human auditory system was not designed to listen to sound inside the ear canal. The ear canal is only one of many parts that make up the auditory system.  We have been limiting listeners to audio reproduced by tiny inexpensive transducers inside the ear canal.  This severely limits the listening experience by focusing all the sound into our ear canals. 

Related Medical Literature:





The Issues

  • Regulatory agencies have mandated hard limits on audio devices.
  • Device and peripherals workaround limits by increasing third party headset sensitivity and/or adjust output levels when different headphone impedance is detected.
  • Content creators and distributors under pressure to capture listener attention.


  • EN50332-1 limits output of bundled headset to 100dB SPL
  • EN50332-2 limits audio jack output to 150mVrms into 32 ohms


  • In the ecosystem of today’s third party headsets, there is no correlation between device output voltage and Sound Pressure Level (SPL) produced by the headphones.
  • Users will likely replace bundled headphones with third party upgrades.
  • Users may own multiple headphones with totally different voltage to SPL relationships.
  • Voltage to SPL transfer function of headphone varies over frequencies.
  • Technical issues that causes quality variations;
    • Headphones with an impedance of 64 ohms or higher cannot produce adequate SPL with restricted drive of 150 mVrms input signal.
    • Popular music production is often over-compressed and maximized to 99% of the possible volume in the final master.
    • Digital file formats such as AAC and MP3 create smaller files sizes by removing original content and adds another compression stage to the audio, which further limits the dynamic range of the original music.
    • Listeners want to experience music as it is heard in real life or at live performance and since listening to compressed files with ear buds cannot recreate this experience in the ear canal. 
    • People are listening in public places with ambient background noise, resulting in them turning up the volume.
    • Headphones/ear buds with limited dynamic range will lose subtle low level content critical to a good listening experience.
    • Commonly used voltage divider methods limit signal swing at the audio jack resulting in a loss of audio resolution.
    • Higher acoustic isolation reduces users’ environmental hazard awareness (automobiles, vehicle sirens etc.)

Device and Headphone/Ear Bud Manufacturers

  • Design for higher sensitivities to fulfil user demand for higher SPL playback, frequently mistaken for high quality playback.
  • Design methods to change output voltages when regulatory test load (32 ohms) are not used.


    • User experience varies depending on combination of;
        • Playback device
        • Headphones/ear buds quality
        • Physical fit to the ear
        • Ambient noise levels.
    • Device from one regulatory region will over or under drive headphones/ear buds from another region.
    • Creates frustration for both users and legislators who are trying to prevent hearing damage/loss.

Content creators and distributors

  • Wants to capture listener attention.
  • Work around the limitation of low quality audio experience by increasing perceived loudness.

The Proposals

Why do people turn up the volume when using ear buds/headphones?

  • People can’t hear the music due to low signal-to-noise ratio caused by ambient noise levels.
  • Low quality transducers limiting the bandwidth and perceived loudness of the music.
  • A desire for more bass sound.

What not to do

  • Never limit based on output voltages
  • Never limit based on output current
  • Never limit based on power
  • Do not over-compress original masters
  • Do not choose lowest resolution digital file

What to do

  • Limit output based on sound pressure level (SPL)
  • Limit based on time of exposure
  • Limit content selectively, conserve dynamic range and preserve low level components
  • Limit masking of content by selectively reducing ambient noise components.
  • Provide adaptive transparency/playthru to minimize blocking of ambient sounds representing potential hazards to user
  • Improve Signal-To-Noise ratio intelligently
  • Audio mastering at device or headphone; safety in fidelity
  • Offer options for optimized physical fit of ear buds, for consistent seal

Technologies available to do it

  • Digital headset interfaces enabled by e.g. USB-C allow identification, enumeration and control of headphones/ear buds.
  • Availability of power from digital connectors enables integrated circuits on headphones
  • Ability to place multiple miniature sensors on headphones, such as MEMS microphones for active monitoring of signal level and spectral content.
  • Ability of Digital Signal Processors on device to process sensor data intelligently.
  • Availability of Multiband Dynamic-Range-Control algorithms on output signal chain
  • Availability of dynamic and adaptive noise reduction algorithms
  • Inexpensive tooling options for production of bespoke earbud inserts

How to do it

  • Analog headphones - legacy headphones without means of identification
    • Headphone should have a set limit for the maximum mW to SPL conversion
    • 90dBSPL at 1mW average (target level to be confirmed with standards agencies)
    • If no data was provided or the codec cannot detect the impedance then headphone power should always be limited to 1mW average and peak power less then 3mW. As a comparison to current situation, the headphone amplifier has the ability to output 300mW or more into the headphones
    • Impedance of headphone can be 8 Ohm to 600 Ohm; Typically 16 Ohm to 32 Ohm
    • Device logic flow
      • Connect headphone
      • Get / check metadata
      • Perform automatic DC impedance measurement (8 to 600 Ohm)
      • Host continuously detects AC impedance at various frequencies
      • Determine full spectrum power output to the headphones/ear buds
      • Adapt the sound power to limit peak power output
  • Digitally connected headphones but not necessarily smart headphones
    • Digitally connected headphones to provide accessible characterized specifications
    • Standardization audio communities involved in database creation
    • Device logic flow
      • Headphones identifies itself during connection
      • Headphones communicates the relevant parameters including SPL/mW and ultra-safe threshold
      • Device starts in safe threshold, either from headphone information or through cloud database
      • Measure actual impedance using none intrusive method, possibly using actual playback content
      • Device continuously analyze audio content to determine crest factor and average power
      • Adapt peak power related to crest factor
      • Limit power on headphone to below 90dBSPL.
  • Smart headphones
    • Ability to adapt, process and control the audio signal independent of the connected device
    • Digital interface
    • Capable of fulfilling the safety standards independently
    • Device logic flow
      • Headphone enumerates and communicates abilities to device
      • Device and headphone determine partitioning of digital processing
      • Device output digital audio stream to headphone
      • Device or headphone will dynamically control power level according to content characteristics and the headphone’s characteristic transfer function
  • High end smart headphone -  with integrated sensors, that may be used for health/body/environmental and ambient acoustic measurements
    • Standards body recommendations for acoustic sensor (microphone) placement in headphones/ ear bud
    • Enumeration details must include transfer function from acoustic sensor to ear drum
    • Sensor readings must correlate well with what the ear hears
    • Ability to detect acoustic seal to ear changes and adapt accordingly
    • Enable adaptive noise reduction and cancellation based on environmental noise monitoring (ambient microphones) vs playback content characteristics

How to influence change? Technical Engagements

Safety Standards

  • EN50332 Team,
    • Who from BBQ: Engage through the Cirrus EDI team.
    • What Strategy: Make sure there is buy in from as many end equipment manufacturers as possible to show market/regulatory demand for for hearing protection to be implemented with as little impact to the customer experience.. (White Paper with details etc)
  • OSHA
    • Who from BBQ: TBD
    • What Strategy: Are the thresholds and recommended resolution for them reasonable, are they applicable to consumers etc. Pre-Work needed before making recommendations.
  • CEA (Consumer Electronics Association)
    • Who from BBQ: TBD
    • What Strategy: Investigate to see if there are standards. R3Audio standards currently have specifications for loudspeaker. Make a recommendation for headphone systems.
  • UL (Underwriters Labs)
    • Who from BBQ: TBD
    • What Strategy: Investigate to see if there are standards.
  • Audio Engineering Society
    • Who from BBQ: AES Members
    • What Strategy: Investigate to see if there are standards.

Interface Standards

  • USB Type C - Multiple members of this work team are part of USB
    • Who from BBQ: TI, NXP, Realtek, Cirrus Logic
    • What Strategy: BBQ’ers to work on proposal/white paper and present to USB Device Working Group.
  • Soundwire XL - Multiple members of this work team are part of MIPI
    • Who from BBQ: TI, NXP, Realtek, Cirrus Logic
    • What Strategy: BBQ’ers to work on proposal/white paper and present to MIPI LML group.
  • 3GPP (part of ITU)
    • Who from BBQ: TBD
    • What Strategy: BBQ’ers to work on proposal/white paper and present to MIPI LML group.
    • Have specifications for things like SNR during calls etc. “Quality of sound/service etc” -- need to find the interface in.
  • Bluetooth Working Group
    • Who from BBQ: TBD
    • What Strategy: They have descriptors to communicate the capabilities of headphones. Our work in safety and driver description would be an idea add on.
  • WiFi
    • Who from BBQ: TBD
    • What Strategy: Investigate to see if there are standards that apply directly to headsets.

Operating System Vendors

  • Microsoft
    • Directly part of BBQ. Need to understand current technology and what modifications need to be made support our safety suggestions.
  • Apple
    • Directly part of BBQ. Need to understand current technology and what modifications need to be made support our safety suggestions.
  • Google
    • Directly part of BBQ. Need to understand current technology and what modifications need to be made support our safety suggestions.
  • Linux
    • Not part of BBQ. Need to engage

End Equipment Suppliers

  • Apple
  • Samsung
  • Lenovo
  • Dell
  • HP
  • Acer
  • Asus
  • LG
  • Huawei
  • ZTE
  • Xiaomi

Integrated Circuit Suppliers

  • Mixed signal
    • Texas Instruments
    • Cirrus Logic
    • Realtek
    • Connexant
    • NXP
    • Maxim
    • Analog Devices
    • Dialog Semiconductor
  • Processor suppliers
    • Intel
    • Qualcomm
    • Mediatek

Marketing Engagements


  • Reach out to consumers who use headphones (headsets) with portable media players/phones/etc. Educate and inform consumers on the dangers of over exposure to high volume media content
  • Reach out to the device/product and headphone manufacturers to encourage adoption and promotion of the new hearing-loss protection requirements.
  • Reach out to content creators to promote and encourage the use of higher dynamic range content to lessen the effects of constant high level listening, causing hearing loss.
  • Reach out to the content distributors (Spotify, Pandora, Netflix, etc) and media playback programs (WMP, VLC, Groove, Foobar, etc.) to encourage the use of smart algorithms that limit the volume level based on continuous listening.


Methods to reach the end-consumer

  • Social media campaign using high profile and popular celebrities to warn of the dangers of hearing loss
    • “This is your brain, this is your brain on drugs”
  • Celebrity endorsement of safety regulations.
  • Warning labels on the headphone/headset devices.
  • Web/Print articles and advertisements evangelizing the dangers.
  • Audible/Visual advertisements (PSA’s) to warn of continued exposure to high volume (Spotify/Pandora/etc.)
    • “The More You Know”
    • Talk shows
    • TED Talk episode
  • Use “headphone only” EDM rave parties to reach young users.
  • Encourage media playback programs to reward the end user to reduce the volume (Nest leaf, Ford Fusion Tree, etc.)
    • Possible reward end user with free music?

Methods to reach the device/product/headset manufacturers

  • Professional publications
    • LinkedIn articles
  • Targeted advertisements
    • DICE/Monster/etc.
  • BBQ representatives to evangelize inside their companies
    • Apple/Samsung/Google/Dell/Lenovo/HP/Asus/Acer/Microsoft/Amazon
  • Articles written and published to industry conferences (conventions)
    •  AES/CES/Computex/IDF/NAMM/IFA/MobileWord Congress/RIAA
  • Help with marketing of improvements in sound quality if regulations are adopted.

Methods to reach content creators

Methods to reach content distributors:

  • Plea to corporate social responsibility to advertise about hearing loss dangers.
  • Reach out using philanthropic organizations (e.g. Gates Foundation)



PCM - CD-A audio files.jpg

MP3 files.jpg

section 7

next section

select a section:
1. Introduction
2. Workgroup Reports Overview
3. The Smartest Person in the Room is the Room: Applications for Virtual and Augmented Music Production
4. Audio Of Things: Audio Features and Security for Smart Homes/Internet of Things
5. A Brief History of Time
6. This Ain’t Your Mom’s Horn Tone
7. Protecting Tomorrow’s Ears
8. Schedule & Sponsors