Active Noise Cancellation Vs Passive Noise Cancellation
What is noise?
Before we get into how noise cancellation and noise isolation works, it’s a good idea to get a little background and consolidate some terms. What is noise? Noise is said to be any signal that interferes with the useful signal. Buff! what a mess these people from the RAE are. To make it easier in Culturasonora we will define it as any sound phenomenon that interferes with listening on our devices, whether it is the sound of the environment or any other sound or music that prevents us from listening as God intended through our headphones.
What is noise cancellation?
What is noise cancellation? It is the cancellation and/or attenuation of the sound phenomenon that we have defined as noise. Between you and us: block out any outside sounds that might annoy us with our favorite track.
What is passive noise cancellation?
What about passive noise cancellation? In fact, strictly speaking, there is no such thing as passive cancellation. What actually exists is an acoustic design of the headphones that allows attenuation and/or control of outside noise. Today, it is the most widely used technology in hearing aid design due to its low cost. Passive cancellation techniques are commonly known as acoustic isolation systems and their mission is to prevent external sound from entering our auditory system. For this purpose, it is usual to interpose insulating material between the casing or external part of the earphone and the part that will be attached to our ear or ear.
It is the simplest, cheapest and most commonly used technology in headphones. However, it has the disadvantage that it does not totally cancel outside noise, but only attenuates it (in values ranging from 8 to 20 dB). Their effectiveness depends on several factors such as the materials used, whether the headphones completely surround the ear (circumaural design), only partially surround the ear (supra-aural design), or are inserted into the ear canal (intra-aural design). This method of noise cancellation may not be the best performing at low frequencies (below 100 Hz) but it is the most economical.
There are two ways to passively isolate sound:
- Some over-ear (circumaural) headphones: these are headphones specialized in external noise isolation. Its ear cushions surround the entire ear with insulating materials and exert more pressure than other helmets around the ear to block sounds. These are usually circumaural headphones with a closed design. They completely surround the ear, relatively isolating it from outside noise.
- The other way to achieve passive noise isolation is to use so-called In Ear headphones, which are inserted directly into the ear canal. The In Ear for professional use provide excellent isolation from the outside. The effectiveness of In Ear (also called In-The-Ear) hearing aids will depend on how tightly they fit in the ear canal in a way that prevents external noise leakage. These earphones are very small and seal the ear canal effectively. They are ideal for walking, swimming and any outdoor activity, as they are very light and compact.
ANC headphones: What is active noise cancellation?
With headphones that allow active noise cancellation we can speak of noise cancellation itself, because headphones of this type detect the external noise signal and recreate it through an electronic circuit by inverting its polarity. As a result, noise is totally or partially cancelled. This is how they work.
The image shows two signals in reverse. To put it simply: it is as if both frequencies were cancelled out and as a result we had no audible signal. In the beautiful theoretical world this works perfectly: both signals are exactly the same with the difference that one is inverted relative to the other, resulting in total silence. However, in the real world, it does not work exactly the same way, as the type of noise will change depending on where we are.
On the other hand, headphones with active cancellation must have at least one microphone to detect external noise. Obviously, cancellation will depend in part on the quality of the microphone, as well as on the electronic circuit that copies the noise signal, thus generating a signal identical to the noise, but inverted. Generally, active hearing aids are very effective when the noise is constant and does not vary in high, mid and low frequencies.
Which is better, active or passive noise cancellation?
The best choice will always be a sum of both: active noise cancellation works best with low and mid frequencies, while passive cancellation isolates high frequencies better. So the sum of the two will always give the best result in terms of total noise cancellation. The cups of circumaural (over ear) passive noise cancelling headphones are usually made of rubber layers that increase the weight of the headphones in order to reduce noise by 15 to 20 dB.
These in-ear and over-ear headphone isolators (intra-aural and circumaural) have their limitations. For example, an aircraft engine can generate noise of up to 80 dB, which makes the insulation insufficient. If you really want to cancel noise, the solution is to buy headphones with active noise cancellation. They do the same as the passive ones but in a more efficient way. They create a barrier that cancels high waves and also have electrical systems that allow them to erase low frequencies.
As an inexpensive option we can consider a pair of in-ear or earplug headphones, which, if they fit well, will isolate us from a good part of the noise. If we want near-total noise cancellation and the size or price of the headphone is not an issue, then you may want to consider purchasing a headset with active noise cancellation.
To see the selection of sound culture noise canceling headphones you can visit: Best Noise Canceling Headphones 2022. We also recommend you review our guide on how to prevent hearing loss at this link. We leave you with a video that explains why noise cancelling technology helmets are having such an impact.