A headphone or earbud box is covered in numbers, and most of them are not sound-quality claims at all. "20Hz to 20,000Hz" describes a range of frequencies the driver can theoretically produce, not how good it sounds. "40mm driver" describes a physical size, not a performance guarantee. "IP54" describes resistance to dust and water, not audio quality at all. Understanding what each number actually measures, and what it does not measure, is the difference between comparing products meaningfully and being talked into a purchase by numbers that sound impressive but tell you almost nothing on their own.
Why manufacturers print these numbers at all
Buyers ask for specs, so brands print specs. That does not mean every number printed is equally meaningful, or even meaningful at all outside a lab. Some of these figures are genuinely useful once you know what they measure. Others are close to marketing filler dressed up as data. Below is the honest read on each one, without inventing a verdict about how any specific product actually sounds, because that requires hearing it, and we have not heard the products discussed on this site. This is also why How to Choose Wireless Earbuds Without Trusting Anyone's Score treats spec literacy as one of only five things worth checking before you shop, rather than the whole decision.
Frequency response range: the most printed, least useful number on its own
A box that reads "20Hz to 20,000Hz" is stating the outer edges of what the driver can theoretically reproduce, from deep bass to the highest treble a healthy young ear can typically detect. Almost every headphone on the market prints a similar range, because the range alone is cheap to claim and easy to round to a familiar figure.
What the range does not tell you: how evenly those frequencies are reproduced. A driver can technically hit 20Hz while producing almost nothing audible at that frequency in practice, or it can hit a range but boost certain frequencies far above others. The number that actually shows this is a frequency response graph, not the range, and that distinction is covered in full in Frequency Response Range vs Frequency Response Graph.
Driver size: bigger is not automatically better
Driver size, usually given in millimeters, describes the diameter of the component that physically moves air to create sound. It is genuinely true that, as a general pattern, a larger driver can move more air and has an easier time producing strong bass. It is not true that a larger driver automatically means better sound overall.
Tuning, the materials used, the enclosure design around the driver, and how well the whole thing is engineered together matter as much as, or more than, raw size. A well-tuned smaller driver can outperform a poorly tuned larger one. Treat driver size as one input among several, never as a standalone quality score.
Water and dust resistance ratings: a real, verifiable spec
Unlike frequency response range, an IP rating (Ingress Protection rating, an international standard) is one of the more genuinely verifiable numbers on the box, because it follows a defined test standard rather than a marketing framing. The first digit after "IP" covers dust resistance on a 0-6 scale, and the second covers water resistance, generally on a 0-9K scale, with higher meaning more resistant in that specific category. An IP54 rating means meaningful dust protection and resistance to splashing water from any direction; it does not mean the product is safe to submerge, and manufacturers are specific about which activities the rating covers, such as sweat and rain versus full submersion. Apple's own published rating for AirPods 4, for example, is IP54, stated specifically as resistant to dust, sweat and water for non-water sports and exercise, not for submersion.
Always read what the manufacturer states the rating actually covers for that specific product, since the number alone does not describe real-world durability under all conditions, only the specific lab test it passed.
Active noise cancellation (ANC) claims
Marketing language like "twice the noise cancellation" or "40dB of noise reduction" sounds precise but is rarely comparable between brands, because there is no single, universally applied testing standard that every manufacturer follows the same way. A claimed dB figure from one brand is not necessarily measured the same way as a claimed dB figure from a competitor. Read any ANC claim as that brand's own marketing framing rather than a number you can directly compare across products, unless you can confirm both figures were measured under the same independent test. AirPods 4 vs AirPods Pro 3: Open Fit or Sealed walks through a concrete example of this: why one has full ANC and the other does not, and why that comes down to fit rather than a marketing tier.
What none of these numbers can tell you
No printed spec, on its own, tells you how something actually sounds, how comfortable it is after two hours, or how it will hold up after a year of daily use. That requires either hearing it yourself, trying it in person, or reading an outlet that has done real instrumented measurement and controlled listening, such as RTINGS or What Hi-Fi. We have not heard the products discussed on this site, and rather than invent an impression, we point you toward outlets that have the equipment to measure it honestly.
A quick reading guide
| Spec on the box | What it actually measures | What it does not tell you |
|---|---|---|
| Frequency response range (e.g. 20Hz-20,000Hz) | The outer edges of frequencies the driver can theoretically produce | How evenly those frequencies are reproduced; see the graph, not the range |
| Driver size (e.g. 40mm) | The physical diameter of the sound-producing component | Overall sound quality; tuning and build matter as much |
| IP rating (e.g. IP54) | Dust and water resistance under a defined test standard | Real-world durability under every condition; read what the brand states it covers |
| ANC claim (e.g. "up to 40dB") | The brand's own stated noise reduction, measured under its own conditions | Whether it is directly comparable to a competitor's claimed figure |
FAQ
Does a wider frequency response range mean better sound?
Not by itself. A wider printed range is easy to claim and common across the market. What determines perceived sound quality is how evenly the frequencies within that range are reproduced, which is shown by a frequency response graph, not the range alone.
Is a 40mm driver always better than a 10mm driver?
No. Larger drivers can move more air, which helps with bass, but tuning, materials and enclosure design matter just as much. A well-engineered smaller driver can outperform a poorly tuned larger one.
What does IP54 actually protect against?
An IP54 rating means meaningful protection against dust ingress and against water splashed from any direction, such as sweat or light rain. It does not mean the product can be submerged; check the manufacturer's own statement for what activities the rating is meant to cover.
Can I compare ANC dB claims between two different brands?
Not reliably, because there is no single testing standard every brand applies identically. A claimed figure from one brand is that brand's own measurement under its own conditions, not necessarily comparable to a rival's claimed figure.
Where can I find real sound-quality comparisons if the spec sheet does not tell me?
Outlets with instrumented measurement rigs and controlled listening panels, such as RTINGS, SoundGuys and What Hi-Fi, publish that kind of testing. We have not heard the products discussed here ourselves, so for the sound-quality question specifically, their measurement pages are the more reliable source.