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What You Really Need to Know About Bluetooth Audio

Author: Evelyn

Mar. 07, 2024

135 0

Tags: Sports & Entertainment

Bluetooth drives wireless headphones and portable speakers and lets you wirelessly connect your stereo system or soundbar to your smartphone and its myriad streaming services. Yet despite Bluetooth’s ubiquity, it’s still the most misunderstood audio technology. Audio companies offer numerous variants—or codecs—of Bluetooth, and some people claim that a certain codec will improve Bluetooth sound quality. But those differences are hard to quantify and harder to hear. Read on if you’re confused about how (or if) different Bluetooth codecs should factor into your headphone or speaker choice.

One important thing to note right from the start is that the Bluetooth audio technology you’re hearing has a much smaller effect on sound quality than the design of the device itself. If you try different wireless headphones or speakers, you’ll hear obvious differences. If you try different Bluetooth codecs, the difference will be small and possibly inaudible. (You can test this yourself using my online Bluetooth blind test.)

In other words, you should choose Bluetooth headphones or speakers based on their fundamental sound quality—as reported in reviews or as you’ve determined yourself—and not based primarily or even secondarily on the Bluetooth audio technologies they support. The codecs don’t make a big difference.

Bluetooth audio codecs explained

In audio devices, the key difference in Bluetooth implementation involves which audio codec they use. A codec (short for “compression/decompression”) is a complex algorithm that processes audio data to make it smaller so it’s easier to send over the Internet or wirelessly from your phone to your headphones. You’ve probably heard of some popular codecs used today, including SBC, AAC, aptX, and MP3. Using a codec is necessary because the less data Bluetooth needs to transmit, the more reliable the connection is—and the less likely your headphones are to lose the signal in the middle of Billie Eilish’s “Bad Guy.”

These codecs are called “lossy” because they discard most of the audio data. Typically, they reduce the 1,411-kilobits-per-second data rate of CD-quality audio to around 300 kbps. The discarded data represents audio that the human ear is less likely to detect, such as a soft sound in the presence of a similar but louder sound. Some codecs allow higher data rates, thus requiring less compression and offering the potential for better sound.

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Many people believe that transmitting an audio signal via Bluetooth will always degrade sound quality, but that’s not necessarily true. If an audio signal is already compressed in a certain codec, and the source device (such as your phone, tablet, or computer) and the “sink” device (such as a wireless speaker or headphones) both support that codec, Bluetooth transmits the encoded audio unaltered, so the sound is the same as you’d get without Bluetooth. The most common example is with Apple Music, which uses AAC, and iPhones, which support AAC. If you use these two things along with a wireless speaker or headphones that also support AAC, Bluetooth will not impact the sound quality. If at least one of the devices doesn’t support AAC, the AAC data is decompressed and then recompressed with another codec, such as SBC. This process can reduce sound quality, although the difference will probably be subtle.

A few codecs claim “high resolution” because they can handle data at resolutions higher than the CD standard, which is 16 bits at a sample rate of 44.1 kilohertz. However, we consider high-resolution support to be more a marketing claim than a useful feature here. It would benefit you only with high-resolution files from a high-resolution streaming or download service, and only if your headphones or speaker can reproduce the claimed extra fidelity—and when the codec is discarding so much data anyway, the benefit of giving it even more data to throw out is questionable.

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Another characteristic that distinguishes codecs is latency. The time it takes for a digital signal processor to decode the encoded audio is often sufficient to delay the audio to the point where it creates lip-sync problems when you’re watching video. Some codecs, such as aptX, are less math- and memory-intensive and thus have less latency. More math- and memory-intensive codecs, such as AAC, may have greater latency but may be more efficient at conserving data and thus may produce better sound quality for a given data rate. There are always trade-offs with codecs.

(Here I should disclose that I worked as marketing director for Dolby Laboratories from 2000 to 2002 and was involved in promoting AAC, but I have had no financial interest in the company or the technology since I left.)

Bluetooth also comes in different versions, such as 4.1, 5.0, and 5.1, but these generally address data-transfer issues and rarely affect audio quality. The only exception I can think of is that newer versions might make transmission a bit more reliable, which could conceivably allow a scalable codec such as aptX Adaptive or LDAC to run at a higher data rate.

Bluetooth audio codecs compared

Here are the audio codecs found in Bluetooth devices. To activate these codecs, you may have to go into your phone’s audio settings. In Android phones, you can typically find codec selection in the Developer Options menu.

SBC: You can find SBC in all Bluetooth devices. If your source and sink devices can’t both support some other codec, the connection defaults to SBC. This codec can run at data rates as high as 345 kilobits per second. If the source and sink devices can both process the audio at a high data rate, the sound quality is hard to distinguish from that of AAC or standard aptX. I’ve measured its latency at around 200 milliseconds, and as much as 300 ms with true wireless earphones—enough to create the potential for lip-sync problems when you’re watching video.

MP3: The familiar MP3 codec is rarely used in Bluetooth, but it is found in a few Bluetooth devices. Technically, it falls roughly between SBC and AAC in audio quality, although the difference is tiny or imperceptible. However, if your phone and your headphones or wireless speaker support MP3, it can yield a minor advantage in sound quality with MP3 downloads or streaming services (such as some Internet radio stations) that use MP3.

AAC: Basically a more advanced version of MP3, AAC generally offers slightly better sound at a given data rate than MP3 and SBC do. With Bluetooth, AAC runs at a maximum of 250 kbps, and though I haven’t yet had a chance to measure its latency, it’s likely at least as bad as SBC’s because AAC’s advanced coding techniques demand more processing time. If you have an iPhone or iPad, having AAC in your headphones or wireless speaker can be a mild advantage for the reasons explained above. However, unlike the aptX codecs, AAC implementation isn’t policed by a single company, and as a result it may be inconsistent in Android phones.

aptX: This codec, offered in Qualcomm Bluetooth chips, differs from most others. Rather than encoding a specific level for each audio sample, it encodes the difference in level between one audio sample and the next. This approach allows it to run faster and achieve lower latency. My measurements show that its latency is typically around 120 ms, which reduces the possibility of lip-sync error compared with SBC. Unlike SBC, which may run below its maximum data rate, the data rate for aptX is always 352 kbps, so there’s a certain guarantee of quality, but any audible difference between aptX and SBC is typically small or imperceptible. aptX has never been available in Apple devices, but it is included in many Android devices.

aptX HD: This is a high-bandwidth version of aptX that runs at a data rate of 576 kbps, and as you may notice if you take my Bluetooth blind test, the difference can be appreciable. With high-quality headphones that can reveal this difference, plus an Android phone that supports the codec, aptX HD is nice to have. I haven’t had a chance to measure aptX HD’s latency, but it’s scalable depending on the application.

aptX Low Latency: With aptX LL, my measurements show latency below 40 ms, which eliminates the possibility of lip-sync errors caused by the codec. This codec became widely available only a year ago and still isn’t available in many audio devices. We hope to see it work its way into TVs, where it would provide an obvious benefit. It would also be great for tablets, but we likely won’t see it in iPads because (like the other variants of aptX) it’s not available in Apple devices. Like standard aptX, it runs at a fixed data rate of 352 kbps.

aptX Adaptive: This new codec should start making its way into products in 2020. It promises to automatically adjust its operation for the best blend of audio quality, low latency, and reliable transmission. Its data rates run between 280 and 420 kbps, and its latency is said to run between 50 and 80 ms.

LDAC: Sony’s LDAC offers the potential for the best possible Bluetooth sound quality. It runs at 330, 660, or 990 kbps; your phone may let you prioritize sound quality (990 kbps) or connection reliability (330 kbps). LDAC is available on many Android phones, but not in Apple devices. I have yet to evaluate its latency, and Sony doesn’t publish a spec. I’ve seen claims that, because LDAC is a sort of hybrid of the technologies used in aptX and conventional codecs such as AAC and MP3, it offers relatively low latency, but I haven’t found any substantiation of those claims.

LC3: Also called Low Complexity Communications Codec, LC3 is part of the new Bluetooth LE Audio standard introduced at the CES 2020 trade show. It is said to achieve higher sound quality than SBC, or comparable quality at lower power, which would extend battery life. Products using LE Audio are expected to emerge in late 2021 or 2022.

Once again, the differences in sound quality among these codecs are subtle at best. This is why we don’t make the inclusion of certain codecs a major factor in evaluating Bluetooth headphones and speakers. The acoustical tuning of the speaker or headphone drivers and enclosure, and the tuning of the device’s digital signal processor, have an exponentially greater effect on sound quality—and your day-to-day enjoyment of your audio gear—than the Bluetooth codec does.

Summary of 30 frequently asked questions-Bluetooth Headphones/earphones (FAQ) and answers including how-to and troubleshooting for Bluetooth Headphones.

TOP 1. What if the headphone is unable to turn on, or turn on without flashing?

  1. Maybe the headphone is out of power that it needs to be fully charged. If charged for more than 30 minutes and there is still no light flashing. Maybe there is something wrong with the battery. 
  2. There is something wrong with chip data. You can try to restore the factory default settings. 
  3. Exclude human factors (such as water damage, getting wet, and so on).

TOP 2. What if the headphone can’t be searched for or connected?

  1.  Misoperation. The headphone is on, but still does not enter the status of being searched. Please note that only when the red and blue lights flash can it be searched for. 
  2. If the red lights and blue lights alternately flash, (geek is that the blue light keeps on) but the phone can’t search for it yet, you can try as follows: (1) Turn off the phone Bluetooth, reboot, and search again; (2) Restart the phone and search again. (3) Every chip of the products owns a memory function. That is to say, every headphone can be repaid with the device that was paired with before automatically. However, the storage spaces of every chip can memory up to 6 to 8 devices. If headset pairs with devices exceed their limitation, they can be searched for anymore. Please restore the factory default settings of the headphones, and connect again. If it fails, it may point to the problems of the headphone signal ending, which we should offer an exchange or refund. 

TOP 3. What if the headphone can be searched but unable to be connected?

If you can search the Bluetooth headphone in your phone but can’t connect them. Firstly, you should exclude that the headset had been paired with another cell phone before. (Please note that if the headset had been paired with another cell phone and this cell phone does not turn off its Bluetooth. The headset would pair with this cell phone automatically) You need to delete the phone-connected records, restart it and reboot the headphone pairing mode so that it can be searched and paired.

TOP 4. What if it always prompts that the PIN code and matched password are wrong when the phone is searching and connecting?

  1. Try to input "0000".
  2. Maybe there is something wrong with Bluetooth data in your phone. You need to delete the phone-connected records, restart it and reboot the headphone pairing mode so that it can be searched and paired. 

TOP 5.What if sound cuts in and cuts out?

  1. Phone or headphones is of a low battery, please charge them fully. 
  2. The distance between the phone and headphones is too far (within 10 meters) or there is obstruction resulting in an unstable signal, such as WIFI and so on. In this situation, please reboot the headphone, fully charge them and try it again anywhere without signal interference. 
  3. While walking, please put your phone and headphone in the pockets on the same side. 
  4. Clear all the devices paired before. Turn off the Bluetooth of the cellphone. Try to reboot and reconnect. 
  5. The signal of the cell phone varies according to the cell phone brand. iPhone is the best one and then goes Samsung in current marketing. The Bluetooth of other unknown cell phones is weaker. If Sound cuts in and cuts out, please try to pair it with other cell phones with better signals.  

TOP 6. What if the sound is delayed?

  1. The low battery of headphones will lead to sound delay. 
  2. it’s related to the way Bluetooth works. Bluetooth sampling rate and error rate would be damaged during the time when the cell phone audio is processed to Bluetooth phone to be accepted and decoded. 

TOP 7. What if there is no sound?

  1. No sound when making a phone call or listening to music. 
  2. No sound in the headphone or in the microphone. 
  3. Make sure both mobile audio and media audio are turned on first and reboot the cell phone if there is still no sound.4. Restore the factory default settings of the headphone. 

TOP 8. What if there is no sound on one side of the headphone?

  1. Headphone data errors occur to restore the factory default settings of the headphone. 
  2. Bluetooth data errors occur in the cell phone reboot the cell phone. 
  3. If all methods fail, the circuit of the speaker may be damaged by human factors or exogenic forces. 

TOP 9. What if the headphone cannot hold a charge?

  1. Figure out what kind of charger is used to charge. Please use other charging cables to charge. 
  2. The light is on or not when charging?
  3. It could be a battery problem if the light still isn’t on after charging the headphone for more than 30 minutes.  

TOP 10. What if the battery doesn’t last as long as described?

The electric quantity of the new headphone is not activated to maximization. It is suggested that you fully charge and discharge the battery a few more times. The actual use of electricity is affected by many factors, such as the volume level of the sound, the distance of connection, the strength of the signal…… So the actual usage time depends on the usage methods and strength.

TOP 11. What if you cannot skip songs?

  1. Maybe the player of the cell phone did not activate the function of skipping songs by wire. Please check the skipping songs by wire in the setting of the player. 
  2. The player is not compatible. Try on another player or another cell phone, and see if it works. 
  3. Please check all settings, and then the earphone, at last goes to skip the previous song/next song. 

TOP 12. What if the headsets do not display full power?

The power displayed on the phone is inaccurate because there is something wrong with the power-displaying firmware. The indicator turns blue when charging is completed. You can observe how long the headset lasts and whether it lasts as advertised.

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TOP 13. Why cannot charge the Bluetooth headphone with charge pal?

In general, charge pals are with current protection. The battery capacity of the Bluetooth headset itself is small. Electric current is small at about 70MA ~ 2MA while charging, which is lower than the saturation current detection range of mobile power. Therefore, it may be mistaken that the headset is full of power when charging it by charging a pal. Because the charging electric current is small, the charge pal will automatically turn off the 5V output. Explanation: To judge whether the headset is charged fully is based on the size of the charge current.

TOP 14. What if the switch function of the Input Method is unavailable after connecting the Bluetooth speaker to my cellphone?

Please use the speaker to enter into Photo Mode, then exit.

TOP 15. The ways to connect with PC.

  1. For computers with Bluetooth capability: (1) Right-click the Bluetooth function and click "search for devices". (2) Select the searched device. (3) Click "pairing". (4) Select the device and right-click the device name. (5) Click "search service". (6)Select "mono/ high-quality audio".
  2. For computers without Bluetooth capability: (1) Insert the Bluetooth adapter. (2) Install Bluetooth Driver (such as IVT). (3) After successfully installing, there will be a Bluetooth icon on the right-hand corner, click to initiate the Bluetooth function. (4) After the icon turned blue, right-click to display the classic interface. (5) Right-click to select "search for devices". (6) Right-click and select "pairing" after searching for the corresponding device. (7) Right-click the device name to select "search service" after successfully pairing. (8) Select "mono/ high-quality audio".
  3. For Apple computers or laptops: (1) Select “set” and choose "Bluetooth". (2) It will automatically search for device and click "search for Bluetooth". (3) Select the device name to pair.

TOP 16. What if there is no voice prompt suddenly?

Connect to your cellphone to check if it still has no sound while listening to the music. If so, the circuit of the speaker may be broken. If it has sound, then it may be because you’ve closed the voice prompt function. Please long press the volume+ button for 3 seconds on the pairing mode to initiate the voice prompt function and long press the volume- button for 3 seconds to turn off the function.

TOP 17. Can it connect to a telephone or TV?

Yes, it can be connected to Bluetooth-enabled devices.

TOP 18. About connecting to third-party software.

  1. The Bluetooth headphones support the audio output function of third-party software (maybe it will incompatible with some software as they haven’t dealt with the Bluetooth module, but this is caused by the software itself).
  2. Most cell phones have both conversation volume control and music volume controls. The conversation volume is the same as third-party software. If you hear low volume coming out from the headphone. Please make sure the following two settings are right. (1) Turn up the volume while having a conversation. (2) The headphone is connected to the cellphone, namely, you’ve connected both the cellphone audio and Media audio.
  3. Make sure you’ve adjusted to the appropriate volume and put the bottom of the headphone right to your mouth to get the better effect.4. Suggest selecting the receiver mode while using the third-party software to play. 

TOP 19. About when connected to the second cellphone after disconnecting the first one.

It is because you haven’t successfully connected it the first time, then you failed to reconnect it after disconnecting. The failure is caused by the signal disruption when you first connect it, you may delete the device from your cellphone, turn off the Bluetooth function and then begin to search to connect it again.

TOP 20. How to use Skype with Bluetooth headphones/Earphones?

When using Skype, you need to set the audio source of the microphone and loudspeaker to "Bluetooth SCO Audio".

TOP 21. Cannot use the built-in FM Radio of the cellphone after being connected to the Bluetooth headphone.

It may be because the cellphone has no built-in broadcast antenna, you need to insert the wired headphone to act as the antenna.

TOP 22. What if the music stops when playing games at the same time?

It may be caused by the gaming software as it invoked the audio channel.

TOP 23. Will the data network or the speed of Wi-Fi be impacted after being connected to the Bluetooth headphone?

No, it won’t. The data network or the upload/download speed of Wi-Fi has something to do with the signal of the network, you can try to turn off the Bluetooth to test.

TOP 24. Problems with connecting to iWatch.

The iWatch is an output device of Bluetooth device itself, so it will not work after being connected to the Bluetooth headphone.

TOP 25. Problems with TWS are constantly disrupted by the environmental interfering signal.

This is caused by the underlying CSR chip, currently, the manufacturer of the CSR chip is undertaking this, but still has no improvement.

TOP 26. How to restore the factory default settings of headphones?

The operation of how to restore the factory default settings of headphones is related to the design of the products from different manufacturers. There are different operations with different designs and specifications. If there is anything we can help with, please contact our customer service team. QCY earphones usually press the reset button for 10 seconds.

TOP 27. What if the headset does not fit comfortably or falls out during sports?

  1. Try to adjust the wearing angle and the depth of the ear. Please try different earbuds if there are to fit you comfortably. 
  2. Everyone has different head sizes and ear shapes. We have tried our best but still could not meet everyone’s requirements. If the headset does not fit comfortably or falls out during sports, please feel free to contact us, we will recommend another headset for you to another try. 

TOP 28. What is the lifespan of wireless earbuds?

You should get roughly two years out of cheap or average-quality earbuds. Best wireless earbuds can endure for four or five years if appropriately purchased. Furthermore, earbuds have a 2 - 4 year average lifespan.

TOP 29. How does noise canceling work on earbuds?

Noise-canceling earbuds listen to the environment and block out undesirable noise before reaching your ears. Tiny microphones inside the earpieces or earbuds respond to the outside sound wavelengths and generate the absolute reverse signal, thus "canceling out" both noises.

TOP 30. How should true wireless earbuds be cared for?

It seems to reason that if you care for and use your true wireless earbuds properly, they will last longer. Keeping them stored in a case and clean when not used is especially important with earbuds, which can be fragile and prone to tears or become clogged with ear wax. Earbuds can last for months or years, depending on how well they are cared for. True wireless earbuds, like over-the-ear headphones, come in various quality and price points, with higher-end models lasting far longer than their budget-friendly counterparts.


If you have any questions about the Bluetooth headset/ earphone, please feel free to contact me. I will try my best to answer them for you. If my personal ability is limited and I cannot answer the questions in time, I will help you consult the electronic, acoustic, and software engineers in our factory to help me answer the questions.

📱 Skype: cloud52020

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What You Really Need to Know About Bluetooth Audio

Summary of top 30 frequently asked questions-Bluetooth Headphones/earphones (FAQ)



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