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Volume and Product Testing Methodology


 
Headphones Safety

A simple analogy for headphone safety is like letting your children use scissors -- while the scissor maker can limit the sharpness and round the edges or tips, some adult supervision will always be required (you don't want them running with scissors or testing how sharp they are on their fingers). Any pair of headphones at any volume is the same concept. As a manufacturer dedicated solely to making children’s headphones, we take numerous measures to reduce overall risk. But, as you’ll read below, there are some limitations to what we can do. Try not to run with scissors and try not to listen to any headphones on maximum volume.
  

 
Short Version

    1. Our headphones are thoroughly tested for both their assembly and their volume levels

    2. Still, for volume levels, different devices output different power levels so the actual loudness can vary either higher or lower than what our tests (based on European Standards) shows.

    3. We use the EU standards because as of now, there isn’t a USA standard or requirement pertaining to volume levels.

    4. For those reasons we recommend parental supervision for all headphones (including ours), refraining from maxing out the volume, using the tablet’s or phone’s built volume limiter if applicable, and taking breaks every every or so.

    5. We’re available to chat over email (support@lilgadgets.com) and phone (866.291.8635) if you have other questions or concerns about our headphones or headphone safety in general.

    6. Listed below are our tests, full testing methodology, and more for your perusal.
       

 
Medium Version

Build quality: We go to great lengths to make our headphones pass the Toy Safety requirements (details of tests and methods below). This is voluntary but something we feel is incredibly important since these are for children. Much like for volume regulation, we do a three stage quality control check on the parts: as they come in, in-line during production, and then a final check on the completed products.
 
Volume level: We have incredibly high quality - essentially studio grade - drivers in our headphones. We think children deserve bright and crisp sounds just like adults get to experience. As for the volume level, ours are tested thoroughly to be at 93 +/- 2db under European testing standards (there isn’t a USA standard test at this time). We manually sort through every driver, test 100% of the headphones as they are being produced, and then do AQL methodology when we test the final products. Again, three checks. Now, are they ALWAYS about 93db with all devices? I’ll address that here now...
 
How loud is too loud: Decibel loudness is a mix of both loudness and duration. So theoretically you can do more damage with 85db than with 93db if you listen at 85db for a longer amount of time. The reason we don't tune ours to 85db is because if the headphones are truly 85db by EU standards (and not just marketed that way), the volume is too low to use on planes or in louder/white noise situations, which is when many of our customers intend to use the headphones when purchasing them. We need the headphones to be useful and if your children can’t hear them, they aren’t useful. What we strongly recommend and encourage is to avoid using them on max volume and to limit actual usage as much as possible. Additionally, many devices have a “volume control” in the settings that we suggest setting. If kids are using them for a longer duration, we also strongly encourage taking 10-15 minute breaks every hour or so.
 
So how are headphones louder or quieter than 93db? Wired headphones depend on the power output of the device you’re using to create the sound. But these devices all have different level outputs -- for example, iPhones have an higher output (more powerful amplifier) than Kindles so any headphone will be louder on iPhones than on Kindles. This is why we use the scissor analogy above. We're working on a few things to help make this discrepancy slightly more avoidable and also more transparent for anyone buying children’s headphones, but regardless, parents should check loudness for themselves and use their judgment on the volume levels.
 
As you can or will hopefully see, we are serious about safety testing and transparency of our procedures. If you have more questions, please reach out to us.
 
Phone: 866.291.8635

 
Long Version

We segregate headphone safety into two parts: build safety and volume safety. We establish our guidelines (you’ll see below), do a pre-manufacturing component check for both build and volume specification match, then do in-line quality control to ensure that everything is proceeding as planned, and then finally do post-production quality control (QC). Post production QC consists of unpacking finished goods and using industry standard AQL thresholds (2.5 major, 2.5 minor, 0 critical defects) to test many facets of our product. For example, volume levels outside our threshold are considered “critical” and rejected on the spot. Likewise, we do stress testing from several angles and if the headphones can’t pass those per AQL standards on the final QC, then the lot is rejected. Rejected goods are reworked if possible in order to reduce waste, but if we can’t rework them they are discarded and new goods are produced under the same strict controls.
 
 
Volume Safety
 
Then there is volume safety, which is a common topic we get asked about.  There are many ways to test volume levels but the bottom line is that lower volume and shorter length of use is going to be better. Hands down; no question. That’s why we encourage parents to have children use their headphones with devices in quieter areas when possible. And why we urge  parents to follow the generally accepted idea that frequent breaks at any volume are needed. According to some sources, that means a break every 15-60 minutes.  We also suggest that parents set the volume limiter on the device itself when possible, just one more safeguard against accidental volume increases. But hey, we’re parents too and know that all those perfect scenarios don’t always add up. 
 
That’s where we come in with our volume limiting at 93 db and why we chose that maximum volume level. Of course as with most things, it’s both complicated and simple.
 
First, we worked on our padding and fit of the headphones to create as much passive noise reduction as we could. From there we tested dozens of headphone decibel levels in dozens of situations to see what was tolerable. 85db was great in a library, but useless on an airplane or during a dinner party. 97db was plenty loud for an airplane, but louder than we wanted on our daughters’ ears. If we could have tuned to exactly 91db we would have, but alas, after much trial and error, we couldn’t. In fact, if you ask any honest manufacturer, they will confirm that they have a variance as well. Since 91db was what we felt was the bottom of usefulness in “louder” situations, we settled on 93db and remind parents that the volume shouldn’t be maxed out and time with the headphones should be limited.
 
It’s not a perfect solution but then again, there isn’t a perfect solution at a price point that works for most families. We’re aiming for unique solutions where parents won’t be required to buy overpriced headphones but still can feel comfortable knowing their children’s safety isn’t an afterthought. We care. And we’re constantly working to find the answer that is best for your kids and ours.
 
Given the nature of mass production and manufacturing, there is always the risk of slight variations and defects that somehow find their way through our rigorous checks. We work tirelessly with our quality assurance and quality control teams in the factories to make those outliers as few as possible but if you happen to get one and feel the headphones are too loud or too quiet please let us know (plug: we have a 100% satisfaction guarantee).
 
As for the actual testing, there are two parts to our volume regulation efforts: what standards are used and then how we make sure our headphones match those standards.
 
 
Standards Used
 
Since the US does not have regulations in terms of the volume, we followed the stricter EU standards to create the test. This standard, EN 50332, has two parts.  Part 1 covers “one package equipment,” where the headphones and the music player are supplied together as a unit. Part 2 covers the matching of headphones and players which are sold separately.
 
 
EN 50332:2013 Part 1
 
EN 50332 Part 1 requires a specified test signal to be replayed from the device under test.  The test signal is a pink noise signal which has been filtered to change the spectrum shape and then soft-clipped to reduce the crest factor.  The test signal is recorded or uploaded to the player at a specified level and then played from the player at the maximum volume setting. The sound levels from the attached headphones are measured using a Head And Torso Simulator (HATS) in accordance with the International Electrotechnical Commission’s IEC 60318-7:2011E. (IEC/TS 60318-7:2011(E) describes a head and torso simulator (mannequin) intended for the measurement of air-conduction hearing aids in the frequency range from 100 Hz to 10 000 Hz. The device consists of a head mounted on a torso that extends to the waist. The head is equipped with simulated pinnae and with cylindrical cavities having acoustic impedance terminations and microphones located at positions corresponding to those of the eardrums in a median human adult. It has been designed to provide acoustic diffraction similar to that encountered around the median human head and torso. Here are photos of a Head and Torso Simulator:
 
 
 
 
The HATS is fitted with ear simulators with microphones at the eardrum positions.  The headphones are then positioned over the HATS mannequin and then both the left and right ear are measured by a ⅓ octave analyzer connected to the microphone of the HATS ear simulator. For each ⅓ octave band, the free field response of HATS is subtracted from the value of the pressure level delivered by HATS and then an A-weighting curve is applied.
 
Regarding the test signal, the testing agency uses the simulated noise as defined by and in IEC60268-1. Succinctly, it is a wide range of program material including both speech and music of several kinds with a frequency range of 20Hz to 200 KHz (the commonly stated range of the human audio spectrum). The noise will have a crest factor of 1.8 and 2.2, which is easy to record on various media types. The test signal is the recorded at an RMS value of -10dB (ref 0 dB at full scale) and given in dB (reference 20.0μPa).
 
The sound levels recorded at the mannequin’s eardrum microphones are converted to the equivalent free-field or diffuse field sound levels. The test is repeated five times with the headphones refitted before each test. The sound pressure level shall be determined for each measurement using an minimum time of 30 seconds.
 
 
EN 50332:2013 Part 2
 
EN 50332 Part 2 uses the same programme simulation test signal as Part 1.  When testing a player without headphones, the signal is replayed at the player’s maximum volume setting and the voltage at the player’s headphone socket is measured across a 32 ohm load. The maximum output voltage is an un-weighted true RMS voltage using an average time of 30 seconds or more.
 
When testing headphones without a player, the test signal is replayed from a source through an amplifier to the headphones under test.  The headphones are placed on the HATS or mannequin as in Part 1, and the sound level is measured.  The voltage required to produce a sound level of 94 dB(A) is measured.  When a player producing maximum output voltage of 150 mV or less is combined with headphones which require 75 mV or more to produce a sound level of 94 dB(A), the sound level of the combination must be 100 dB(A) or less.
 
 
 
Factory Calibration Test
 
In order to confirm our factory equipment conforms to the above mentioned EU standards, we first run a calibration test. We are checking our equipment against two values of theirs: (a) the dB at 1K and (b) the average of the entire curve. At the beginning of production of each lot, we recheck the calibration and confirm that it's accurate.
 
Once the factory equipment is confirmed to be calibrated, we then apply it to our production. 100% of our headphones are checked in production by our in-factory quality control team. They are individually checked for both left ear and right ear (minimum five times) by one of our electroacoustic test meters monitored by a trained engineer. We use industry standard, high grade, audio testing equipment that is used in most audio factories worldwide. In our particular case, we wanted to be extra sure that as few headphones as possible pass QC inadvertently so we built a special apparatus that is custom to each model of our headphones in order to produce more accurate tests.
 
Lastly, we unpack finished goods and use the industry standard AQL (2.5 major, 2.5 minor, 0 critical defects) to test many facets of our product, including but absolutely not limited to volume levels. That said, volume levels outside our threshold are considered critical and rejected on the spot. Rejected goods are reworked if possible in order to reduce waste, but if we can’t rework them they are discarded.
 
 
Build Quality
 
Our build quality focus is not to only to make the headphones durable but also to make sure LilGadgets’ products are safe for your child to use. Our products go through thorough testing procedures in order to meet the Standard Consumer Safety Specification for Toy Safety requirements. This is a voluntary certification but something we take seriously because safety isn’t just about ear protection. It’s also about reducing choking hazards on small parts like the in-line microphone on our cables. It's about reducing breakability of large pieces into small parts. We have a custom plastic mix that is much more flexible so full snaps and shattered pieces are extremely rare. It’s about making sure that if your child gets twisted in the cable, it doesn’t create safety concerns. Our cable jacks have the pull force custom tweaked so it balances the need for the cable to stay in securely but pull out at the right time.
 
And there are other little things we’ve done to make the build better and safer on all our headphones (we can't give away all our secrets).
 
  

 
Volume Levels
 

Now that we have established that our headphones are held to the highest standards on the market and we have shown how thorough our quality checks are to ensure those standards are met, how can other tests show our headphones to be softer or louder than what we advertise?
 
The answer is that most countries don’t have a standard test for both how to measure volume levels and quite possibly more importantly, there’s no standard that device manufacturers are held to for their power output. If you use a wired headphone with a device that has a high voltage, you could potentially get louder sounds. When we test, we use the international standard to create 1 mW, which is 32 ohms at 179 mV. But there is a wide spread of devices and their unique power output on the market that aren’t required to follow any output standards. For example, the Samsung S4 is 340mV (Kindles and airlines are lower than the Samsung we believe, but haven’t been able to confirm yet, while iPhones are higher but vary depending on the model). Therefore with our 93db headphones, we could see maybe 95-96db on the Samsung at max. This is where some supervision is required -- we cannot control the device power output unfortunately.
 

 
What We Are Doing

First, we are continuing to quality check endlessly so that what we say we’re selling is exactly what we are selling. Second, we are working on ways to make this volume discrepancy more easily understood to parents. Third, we’re exploring some creative ways through accessories and apps to provide more control over volume levels. Fourth, we’re listening to all the feedback from customers and professionals so we can continue to move towards a more perfect solution.
 

 
Tests Passed

Here are a few of the tests we’ve passed around the world. We only sell one model of each headphone so that model will pass all the associated tests. For example, the Untangled Pro you buy in the USA is the same as the one in Canada or Australia or Taiwan, so it will have passed all the tests required for all those countries for the Untangled Pro. If you have a specific question about tests, please email us at support@lilgadgets.com and we’ll do our best to answer.

  • AS/NZS ISO 8124.1:2016
  • AS/NZS 4268: 2012+A1: 2013
  • CFR 47 FCC PART 15 Subpart C: 2014 section 15.247
  • UN38.3 Lithium Battery Tests
  • ICES (Information Technology Equipment (ITE) – Limits and methods of measurement)-003: 2012 Issue 5
  • 16 CFR 1500.53f - Tension Test (cable)
  • 16 CFR 1500.52c - Bite Test (cable)
  • California Proposition 65
  • ASTM F963-11 Standard Consumer Safety Specification on Toy Safety.
  • Section 101 of U.S. Consumer Product Safety Improvement Act of 2008 (CPSIA) to determine the Lead content in the submitted sample.
  • Phthalates testing under CalProp 65 (DBP,BBP,DEHP,DIDP,DINP, DNOP, DNHP)
  • ETSI EN 300 328 – Electromagnetic compatibility and Radio spectrum Matters (ERM); Wideband Transmission systems; Data transmission equipment operating in the 2.4GHz ISM band and using spread spectrum modulation techniques: Part 2: Harmonized EN covering essential requirements under article 3.2 of the R&TTE Directive.
  • Conformity to NCC set standards and compliance with Taiwanese legal requirements

        Here are our testing facilities:
         
        Thank you so much. And again, please reach out to support@lilgadgets.com with any questions.

         

        Best always,
        The LilGadgets Team

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