A volume limiter literally limits audio output to a specified, safe listening level. They’re a popular feature in kids headphones, but they’re also available in products for adults. Level limiters usually aim to limit the maximum volume to 85dB(SPL) or less.
But how exactly does volume limiting work, is this technology reliable, and do you really need it? Let’s find out.
Why should you get volume-limited headphones?
Headphones can produce sounds of more than 115dB(SPL). That’s equivalent to a rock concert and way too loud for extended listening periods. 80dB(SPL) is a safe volume for all-day listening, but even at that level, your ears need regular breaks.
If you exceed the safe listening time for a specific volume, say more than 30 minutes at 110dB(SPL), you risk noise-induced hearing loss (NIHL).
Read more: What is noise-induced hearing loss?
It’s difficult to tell whether you’re within safe volume levels. Even with the same sound pressure reaching your eardrum, headphones subjectively won’t sound as loud as a loudspeaker because you’re missing spatial and physical cues like bass vibrations and apparent distortion. Since the perceived loudness is lower, many people instinctively turn up the volume when using headphones. What’s worse, when external noise competes for your attention, the typical reflex is to drown it out by further increasing the volume.
Since 2013, all music players sold in the European Union and Switzerland must effectively limit volume output to 85dB(SPL), though users can override the limit and increase the volume up to 100dB.
It might be feasible for an adult to stay aware of volume levels, but it’s tedious. Now, imagine your kid when you use the vacuum or when a sibling makes a ruckus. Volume limiting headphones automatically protect you and your loved ones from listening at dangerously high levels. If you’re not buying your audio devices in the EU or Switzerland, you should consider volume limiting; at least for your kids.
How do headphones work?
Before we dive into the details of how volume or level limiters work, let’s look at the relevant technology inside your headphones. Essentially, headphones transform electrical energy into sound waves, which is exactly how loudspeakers work. Technically speaking, that makes them transducers.
Learn more: How do speakers work?
An amplifier, like that found in your stereo, smartphone, or computer, supplies the electrical power to the headset. With passive headphones, the power of the external amplifier determines the maximum sound pressure level (SPL) or volume.
Digital headphones—i.e., all Bluetooth headphones—contain a digital signal processor (DSP), which processes the digital data received from a playback device, and a digital-to-analog converter (DAC), which transforms the processed digital signal coming from the DSP into an analog electrical signal.
How does volume limiting work?
A hardware volume limiter can either be a part of the headphone or an in-line adapter—usually a cable—that sits between the audio source and the headphone. A software volume limiter is built in as a feature in your smartphone or media player.
Apart from their location, volume limiters can also differ on a technical level. Our audio engineer AJ Wykes explains: There are different approaches to output limiting depending on the complexity and cost of the headphones.
1. Wired (passive) headphones
Passive headphones have no source of power available to do anything “smart,” so they depend on passive components to limit their acoustic sensitivity. That basically means using resistors as a voltage divider to lower the acoustic sensitivity. With resistors in place, you’ll need more power to achieve a given sound pressure level (volume).
This approach assumes that the amplifier driving the headphones will reach the voltage limits imposed by its power supplies before a dangerous SPL is reached by the headphone. If the electrical characteristics of whatever is driving the headphone are known and won’t change, this simple approach can effectively limit the SPL. However, there’s usually nothing stopping the end user from plugging their headphones into a higher-powered amplifier to reach higher levels.
Read more: Why we prefer analog headphones
2. Wired active analog headphones
Active headphones have a battery to power the electronics, typically to provide onboard EQ or active noise cancelling (ANC); though these are rarely analog nowadays, as digital technology is superior and more cost-effective. Devices like this have active amplification stages that drive the transducers. Analog limiting circuits (automatic gain controls) can impose a maximum output voltage to the transducers, calibrated to correspond to a maximum SPL (output volume level).
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This approach can limit the level reasonably well, but there will be a compromise made between “attack time,” meaning the speed at which the limiting circuit reacts to the input signal, other compression characteristics, and transparency (i.e., how badly music and other content is affected by the limiting process).
3. Wired or wireless digital headphones
Digital audio systems have a defined ceiling, or upper limit, that we know the signal can’t exceed. Because of this, the headphone’s DAC and amplification stage can be calibrated so the maximum digital signal level won’t produce an acoustic output from the headphone above a defined threshold. Technically, this is scaling the output, rather than limiting the signal, and can render a lot of audio content too quiet. However, there’s a better approach.
With DSP in the signal path, limiting the level in the digital domain is relatively easy. Digital limiters can be highly effective, as they’re able to “look ahead” at the incoming signal and therefore adjust things quickly and accurately. A well implemented digital limiter can also be fairly transparent, so it won’t impact the listening experience too much.
Is volume limiting reliable?
Not all level limiting is made equal. Resistors passively limit the volume by restricting the amount of power converted to sound. Hence, headphones that rely on this method can surpass safe listening levels when the amplifier, such as your stereo system, is powerful enough. Digital limiters are a little more foolproof, but implementations can vary.
A 2019 study testing consumer-grade headphones for children found that level-limiting results can be all over the place. Some headphones achieve outputs well over 95dB(SPL). With loudness doubling every 10dB, this is actually more than four times as loud as 75dB(SPL); the maximum that ASHA recommends for children.
The study highlights that more powerful devices, such as laptops and CD players, can achieve higher volume outputs, suggesting that these devices used resistors. In Bluetooth mode, however, both tested headphones stayed within safe limits.
Volume limiting headphones for kids and adults
Many headphones for kids feature level limiting. Based on the study mentioned above, we recommend a volume limiting model from Puro Sound Labs; our favorite choice for children is the JLab JBuddies. These headphones are spill-resistant, feature a fun and kid-safe design, and limit the volume to 85dB(SPL).
Related: Best kids headphones
Adolescents might prefer a less flashy design. The Puro Sound Labs PuroQuiet includes volume limiting, ANC, and has decent sound.
Adults have far fewer choices when it comes to volume-limiting headphones. Puro Sound Labs appears to be the only company that offers volume-limiting headphones suitable for adults. At SoundGuys, we have reviewed the PuroGamer model, which also is a great fit for teenagers. Puro Sound Labs’ other option for adults is the PuroPro, a set of hybrid ANC volume limited Bluetooth headphones, which I found too tight for my noggin, but otherwise it was great.
Alternatives to volume-limited headphones
Level limiting headphones can be a pricey purchase. Here are some more affordable options.
Cables and adapters
If you already have a good pair of analog headphones, you could simply switch out the audio cable. Puro Sound Labs, for example, offers 3.5mm auxiliary audio cables that limit the output volume to 85dB(SPL). Keep in mind that since these cables use resistors, a more powerful device might crack the 85dB ceiling.
Another option is to plug the headphones into a volume limiting adapter, which in turn plugs into the audio source.
Since Apple devices max out at 102dB, staying within 70% volume should put you within the safe zone. You can set a hard volume limit under Settings > Sounds (or Sounds & Haptics) > Headphone Safety.
If you want to prevent your kid from lifting the limit, head to Settings > General > Restrictions > Enable Restrictions and add a PIN to lock it in.
Not all Android devices let you set a volume limit, but Samsung phones and several others do. Go to Settings > Sound (or something to that end) > Volume, and, if available, tap the three-dot menu in the top right, then select More options or Media volume limiter. Here, you might be able to turn on the volume limiter and determine a maximum percentage.
If you don’t have this option or want to lock in the limit, you could use an app. Volume Lock offers comprehensive volume control options. While the fullscreen ads can be annoying, they only kick in when you adjust advanced settings.
Both Android and iOS also feature max volume or exposure warnings that alert you when you enter the danger zone. Don’t ignore them, but rather turn the volume down a little, as those warnings usually don’t kick in until around 85+dB(SPL).
Last but not least, get headphones with good isolation or noise cancellation. When you can’t hear outside noise, you won’t feel the need to crank up the volume in the first place.
Learn more: What is isolation?