2023-09-25 14:15:00
If there is a major factor that contributes to increasing the volume of our headphones, it is undoubtedly external noise or “noise”, whether on city streets, in coworking offices, on buses, planes, among others. others. For this reason, many think that the greater the “volume” of the headphones, the greater the quality, which is a big mistake.
To correctly analyze the sound of a headphone, we must be in a quiet environment or have a headphone that can somehow isolate the ambient noise, as this way you will be able to clearly hear what is being reproduced. After all, we will analyze the capabilities of definition, extension, separation, sound stage, among other characteristics, and they do not “play loud”.
What is noise cancellation?
What passive and active noise cancellation (ANC) is and how it works.
There are two types of isolation in headphones, the passive isolation and the active isolation. It is important to know how to differentiate them, because even in a headphone with active noise cancellation (ANC), it is important to have good passive isolation so that it really works as it should.
O passive isolation is one that is done naturally, through one’s own phone structure [1], without wasting any energy. In headphones tipo in-ear [2]it is achieved by inserting the ear tips [3] in the ear canal, effectively attenuating noise. In over-ear and on-ear headphones, isolation is achieved through ear cups (conchas) [1] and the ear pads [3]where both cups and pads (“cushions”) can be made from different materials in order to completely seal the speakers (drivers) [4]. For the sound to sound more natural, the inside of the ear cups must be covered with insulating materials, isolating external noise and dampening the reverberations generated by the headphone driver.
O active isolation is one that is done electronically, through microphones, speakers (drivers) and a circuit for processing the audio with DSP (Digital Signal Processing) [5]. As the energy supply is necessary for this mechanism to work, we call it “active”, as it needs a pair of batteries. In over-ear and on-ear headphones, it is easier to apply, as there is more space in their structure, even enabling superior performance compared to in-ear headphones, as it allows the assembly of more complex projects. In in-ears, we have several problems that can interfere with obtaining a good result in active noise cancellation (ANC), including a very small structure and a good fit, something of extreme importance, which I explained how to do properly in this tutorial.
Headphone structure article
Article about types of headphones
Article about what ear tips and ear pads are
Article about what drivers are and what technologies exist
Article about what is DSP
How does noise cancellation work?
To make the phenomenon that occurs with active noise cancellation (ANC) clearer, it is necessary to understand how the cancellation of sound waves occurs, where the result is silence. To understand the process, it is essential that you know that “frequency” is the length of a sound wave (the distance from one peak to the next or from one side to the other), as everything will revolve around it.
Generally, headphones with ANC usually cancel only one frequency range of the sound. The reason for this is that unfortunately it is not possible to cancel out any ambient noise due to the limitations of the technology itself, as I will explain below.
If we want to “cancel” a frequency range of the sound, we will need to eliminate the troughs and crests of the wave so that it becomes flat (silent). The simplest way to achieve this is to introduce exactly the same sound (frequency), but out of phase. Phase is a word that describes the timing of a frequency. When two waves of the same frequencies occur simultaneously with synchronized peaks and troughs, we call it “In Phase”. When their crests and troughs oppose each other, we call them “Out of Phase.” The diagram below shows our starting frequency and our introduced frequency, both in and out of phase.
Structure of a wave. “In Phase” and “Out of Phase”
When we introduce the same frequency, but “Out of Phase” from the initial frequency, with the valleys and crests opposite the initial frequency, the meeting of these waves will cause the total cancellation of the sound, silence.
Meeting the original “In Phase” frequency with the “Out of Phase” frequency
Active noise cancellation (ANC) basically works through four components. Are they:
Microphones
Noise cancellation circuit
Speakers (driver)
Battery
For ANC (Active Noise Cancellation) to work, a set of microphones are used, positioned externally and internally, to capture external sound and the sound produced by the speakers (drivers). This will serve to provide the audio information necessary for the noise cancellation circuit to process the sound.
The noise cancellation processing chip detects the audio generated by the microphones and generates “fingerprints” of the noise. By doing this, he observes the frequency and amplitude at which the sound wave arrives. Then, analyzing the external and internal sound, an “artificial” wave is created by the processor, which is a version opposite to that of the ambient audio (external sound).
The artificial wave, created by the noise canceling circuit, is then transmitted to small speakers in the earpiece, which are pointed towards the outside of the headphones. This sound generated by the small speakers, being in exact opposition to the external sound wave, ends up canceling out the ambient sound, thus generating silence.
Diagram of how active noise cancellation (ANC or Active Noise Canceling) works.
Why use noise cancellation?
Over time, we become accustomed to the noise of the city, work or during a trip, whether by bus, subway or plane. This makes us forget how stressful and harmful “noise” is to our mental and hearing health.
Noise sometimes takes away our concentration from the activity we are carrying out, for example, at work, where we need to focus well, so that we can think and act more quickly and accurately. Furthermore, noise prevents us from hearing something clearly, from communicating with people like when we are at a concert or when a plane passes by or when we walk near a construction site, for example. As if that weren’t enough, noise can prevent us from getting quality sleep. All of this brings great stress and considerably affects our health.
Continuous exposure to noise can irreversibly damage our hearing health depending on the decibel level (dB) and time we are exposed. Because of this, many people end up buying headphones with ANC without the main objective being to listen to music, but rather to obtain a greater level of silence in their daily lives and be able to carry out their activities more calmly and efficiently. They use this solution when it is no longer possible to isolate external noise passively, as currently the limit for attenuating noise passively is up to 25dB, but there are places where noise reaches, for example, 85dB or even even 100dB, continuously for a long time.
How did the ANC come about?
The inventor of active noise cancellation was Dr. Lawrence Jerome Fogel. He designed the first active noise cancellation systems in headphones and patented his designs specifically for the aviation field because of the high noise levels (decibels) during long periods of exposure, creating tremendous difficulty in communication between airline pilots. jets.
Noise cancellation became popular when researchers at MIT, together with Amar Bose’s Bose Corporation, launched their famous QuietComfort series headphones in the 2000s. Initially, headphones aimed at aviation were created, as mentioned above, but with Over time, the company ended up developing headphones for the common consumer, due to the diverse application possibilities.
Why is noise cancellation called “active”?
Noise cancellation is active due to the need for energy to make the system work. The source of this energy is usually a rechargeable lithium-ion battery.
Does noise cancellation completely block external sound?
Unfortunately not. Even the best over-ear and on-ear headphones with ANC have problems blocking out all types of sounds generated in the environment. Continuous noises are easier to block than sudden/random noises.
There is difficulty with ANC blocking or attenuating sounds that are random, sudden, as there is a delay between capturing the audio, processing it and reproducing the inverted waves through the speakers so that silence is generated. In this case, it is necessary for the ANC headphones to “guess” how the noise will be reproduced before it is even generated. In other words, headphones need to estimate the audio profile of ambient noise to better cancel noise from the location where you are.
Low frequency sounds, such as an airplane engine, car engine, bus engine, have a longer wavelength, are slower and generally tend to be more repetitive. In contrast, high-frequency sound waves, such as babies crying, people talking, incorporate more information, change more frequently, are faster, and are therefore much less predictable and difficult to deal with.
High frequency and low frequency.
Does ANC affect sound quality?
ANC unfortunately influences sound quality. It creates background noise in the music making the sound not sound as natural. Users may also experience a change in air pressure, although there are openings in the headphone cups to allow air moved by the headphone drivers to escape. For these reasons, audiophiles end up preferring headphones that cancel noise passively, as they strive for sound quality.
An example of this interference are the Bose QC35 and Sennheiser PCX550 headphones, which when the ANC is turned off, an improvement in sound quality is noted. However, don’t panic, because in more expensive headphones with ANC, the manufacturer implements internal microphones so that this interference in the music is attenuated. Currently, the headphone with the best implementation of ANC technology is the Sony WH-1000XM5, which can cancel out external sound with minimal interference to the music.
Conclusion
Headphones with active noise cancellation are very useful in the daily lives of many people who suffer from noise in cities, during their work and when traveling. Because of this, there is no denying that ANC is a very tempting feature for many.
However, the benefits generated by active noise cancellation, if well implemented, come with a high cost to acquire with prices ranging from approximately US$250 to US$400 for the best headphones on the market for this technology.
There is also the question of the balance between the sound quality to be lost and the practicality of use to be gained with a headphone sem fio Bluetooth [6] with ANC for everyday life. The user will have to analyze what will bring the most benefits to him according to the weight he will give to the characteristics of the headphones according to the activities he performs in his daily life.
I hope this article has clarified some of your doubts, my dear readers. Comment below what you think!
[6] Article about everything Bluetooth headphones
This article is made in partnership with Grupo Fones de Ouvidos High-End:
1695652692
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