In recent years, more and more headphone and earphone manufacturers have been offering active noise control systems, also known as active noise cancellation. Originally introduced in high-end models, this technology is now available in more affordable devices. The concept of active noise control was patented by the American brand Bose in 1986, initially for professional use in aviation. It allowed helicopter pilots to communicate without being disturbed by the loud noise of the rotor. Over time, this technology has become popular in consumer headphones and wireless earbuds, thanks to advancements in engineering.
Active noise cancellation is achieved by generating sound waves that are the exact opposite of the ambient noise, effectively cancelling it out. This technology works best with continuous sounds, such as the engine noise in an airplane cabin or the rolling sounds in a car, train, or bus. However, it is less effective with unpredictable sounds like voices or keyboard typing, as the system operates in real-time and may not respond as quickly.
One of the key advantages of noise cancellation is that it allows for better isolation, reducing the need to increase the volume excessively and protecting our ears from potential damage. However, not all brands offer the same level of effectiveness in noise reduction. The performance of active noise cancellation depends on several factors. Firstly, having a dedicated chip integrated into the device is crucial. This chip analyzes the surrounding sounds and generates the opposite sound waves. The more advanced the chip, the faster and more effective the response. For example, Sony’s WH-1000X model uses a high-performance chip that can analyze sounds over 700 times per second.
Another important factor is the quality of the microphone integrated into the headphones or earphones. If the microphone is of poor quality, it will send a low-quality signal to the chip, making it difficult to generate the opposite sound waves accurately. The microphones also play a role in achieving a high-quality transparency mode, which allows users to listen to their surroundings without removing their headphones. However, if the microphones are of poor quality, the voices may sound distant or incomprehensible, rendering the transparency mode less useful.
To measure the performance of active noise cancellation, our laboratory conducts tests using binaural microphones placed on a head-shaped dummy. This setup simulates human ears, and external sources play recorded sounds such as airplane engines, train noises, or subway sounds. We measure the volume captured by the microphones first with the headphones off to determine the passive isolation provided by the physical design of the headphones. Then, we activate the active noise cancellation and measure the volume again. The difference between the two measurements gives us an idea of the level of attenuation achieved.
Choosing headphones or earphones with active noise cancellation can be challenging based solely on technical specifications. Manufacturers rarely mention whether their devices have a dedicated chip for noise cancellation or the number of microphones integrated into the product. However, a general rule of thumb is that having at least four dedicated microphones improves the ability to capture ambient sounds accurately. Additionally, opting for reputable brands like Bose, Sony, Apple, or Beats, known for their advancements in this field, can ensure a better noise cancellation experience.
In conclusion, active noise cancellation technology has become increasingly important in the world of headphones and earphones. It provides a means to enjoy music or audio content without being disturbed by external noise. However, it is essential to consider factors such as the quality of the chip, the microphones, and the reputation of the brand when selecting a device with active noise cancellation. By understanding how this technology works and its limitations, consumers can make informed choices and enhance their listening experience.