Active Noise Cancellation: Analog Circuit

Active Noise Cancellation (ANC) is a technology used in many commercial and professional products, one of which are ANC headphones that provide a listener with the comfort of attenuation of ambient noise. ANC is possible due to the wave interference phenomenon and is implemented using a combination of analog circuitry and digital algorithms in commercial headphones. The aim of this project was to explore the possibility of successfully implementing ANC using only analog circuitry. This project concludes that it is possible to implement Active Noise Cancellation using analog circuitry, but such implementation introduces a trade-off between which frequencies one desires to cancel the most. This project also touches on the importance of using a microphone in the ANC circuit that can pick up the noise from a distance and does not introduce much electrical noise to the signal. The circuit that includes a microphone and a pre-amplifier provided 1-4 dB of cancellation in the 80-200 Hz frequency range, little to no cancellation in the 200-500 Hz frequency range, and some noise amplification in the 500-1000 Hz range. The waveform generator fed circuit without a microphone provided over 5 dB of noise cancellation in the 80-120 Hz range, with the highest being 14 dB at 100 Hz. It also provided over 3 dB of noise cancellation in the 120-800 Hz range with some outlying frequencies, and some ambient noise amplification in the 800-1000 Hz range. The results show the possibility of implementing ANC using analog circuitry only, however they also show the trade-offs introduced from the decision to use analog circutry only

Active Noise Control in The New Century: The Role and Prospect of Signal Processing

Since Paul Leug's 1933 patent application for a system for the active control of sound, the field of active noise control (ANC) has not flourished until the advent of digital signal processors forty years ago. Early theoretical advancements in digital signal processing and processors laid the groundwork for the phenomenal growth of the field, particularly over the past quarter-century. The widespread commercial success of ANC in aircraft cabins, automobile cabins, and headsets demonstrates the immeasurable public health and economic benefits of ANC. This article continues where Elliott and Nelson's 1993 Signal Processing Magazine article and Elliott's 1997 50th anniversary commentary~\cite{kahrs1997past} on ANC left off, tracing the technical developments and applications in ANC spurred by the seminal texts of Nelson and Elliott (1991), Kuo and Morgan (1996), Hansen and Snyder (1996), and Elliott (2001) since the turn of the century. This article focuses on technical developments pertaining to real-world implementations, such as improving algorithmic convergence, reducing system latency, and extending control to non-stationary and/or broadband noise, as well as the commercial transition challenges from analog to digital ANC systems. Finally, open issues and the future of ANC in the era of artificial intelligence are discussed.Comment: Inter-Noise 202

Noise Control through Active Noise Cancellation Technique in Mines

A critical analysis of the exposure of miners to high sound pressure level Noise (>90 dBA) is carried out. The Noise Exposure Index of different machine operators is also observed. And a theoretical solution in the form of a specially designed headphone incorporating Active Noise Cancellation and Band Pass Filter is established. The Noise level was found be above the permissible limits in GDK 10A incline and GDK 10 incline for most of the machinery. At face the noise was within permissible limit of 90dBA only at a distance of 20 m in Tirap mine. The machine producing least noise level among those observed was Mine Riding Car in GDK10A incine and the noise level produced was 74 dBA at 20 m. This very high noise level was hazardous for the miners exposed to them as well as it hampered the speech communication inside the mine. A solution to it using conventional headphones has failed because of its inefficiency in allowing desirable sounds of person to person communication and the sound of the alarm of the ‘Roof Fall’. This thesis illustrates a design of special headphone incorporating the techniques of ANC and Band Pass Filters for use in mechanized mines which allows all the desirable sound to pass through but filters out the undesired machine noise. The headphone would facilitate efficient speech communication inside the mines

A Frequency-Domain Method for Active Acoustic Cancellation of Known Audio Sources

Active noise control (ANC) is a real-time process in which a system measures an external, unwanted sound source and produces a canceling waveform. The cancellation is due to destructive interference by a perfect copy of the received signal phase-shifted by 180 degrees. Existing active noise control systems process the incoming and outgoing audio on a sample-by-sample basis, requiring a high-speed digital signal processor (DSP) and analog-to-digital converters (ADCs) with strict timing requirements on the order of tens of microseconds. These timing requirements determine the maximum sample rate and bit size as well as the maximum attenuation that the system can achieve. In traditional noise cancellation systems, the general assumption is that all unwanted sound is indeterminate. However, there are many instances in which an unwanted sound source is predictable, such as in the case of a song. This thesis presents a method for active acoustic cancellation of a known audio signal using the frequency characteristics of the known audio signal compared to that of a sampled, filtered excerpt of the same known audio signal. In this procedure, we must first correctly locate the sample index for which a measured audio excerpt begins via the cross-correlation function. Next, we obtain the frequency characteristics of both the known source (WAVE file of the song) and the measured unwanted audio by taking the Fast Fourier Transform (FFT) of each signal, and calculate the effective environmental transfer function (degradation function) by taking the ratio of the two complex frequency-domain results. Finally, we attempt to recreate the environmental audio from the known data and produce an inverted, synchronized, and amplitude-matched signal to cancel the audio via destructive interference. Throughout the process, we employ many signal conditioning methods such as FIR filtering, median filtering, windowing, and deconvolution. We illustrate this frequency-domain method in Native Instruments’ LabVIEW running on the Windows operating system, and discuss its reliability, areas for improvement, and potential future applications in mobile technologies. We show that under ideal conditions (unwanted sound is a known white noise source, and microphone, loudspeaker, and environmental filter frequency responses are all perfectly flat), we can achieve a theoretical maximum attenuation of approximately 300 dB. If we replace the white noise source with an actual song and the environmental filter with a low-order linear filter, then we can achieve maximum attenuation in the range of 50-70 dB. However, in a real-world environment, with additional noise and imperfect microphones, speakers, synchronization, and amplitude-matching, we can expect to see attenuation values in the range of 10-20 dB

Acoustic, psychophysical, and neuroimaging measurements of the effectiveness of active cancellation during auditory functional magnetic resonance imaging

Functional magnetic resonance imaging (fMRI) is one of the principal neuroimaging techniques for studying human audition, but it generates an intense background sound which hinders listening performance and confounds measures of the auditory response. This paper reports the perceptual effects of an active noise control (ANC) system that operates in the electromagnetically hostile and physically compact neuroimaging environment to provide significant noise reduction, without interfering with image quality. Cancellation was first evaluated at 600 Hz, corresponding to the dominant peak in the power spectrum of the background sound and at which cancellation is maximally effective. Microphone measurements at the ear demonstrated 35 dB of acoustic attenuation [from 93 to 58 dB sound pressure level (SPL)], while masked detection thresholds improved by 20 dB (from 74 to 54 dB SPL). Considerable perceptual benefits were also obtained across other frequencies, including those corresponding to dips in the spectrum of the background sound. Cancellation also improved the statistical detection of sound-related cortical activation, especially for sounds presented at low intensities. These results confirm that ANC offers substantial benefits for fMRI research

Ultra-broadband active noise cancellation at the ears via optical microphones

High frequency noise has generally been difficult to be cancelled actively at a person's ears, particularly for active headrest systems aiming to free the listener from noise cancellation headphones. One of the main challenges is to measure the noise precisely at the ears. Here we demonstrate a new error sensing methodology with an optical microphone arrangement for active noise cancellation (ANC). It can measure the noise accurately for ANC without any obstructions at the listener's ears. The demonstrated system, or virtual ANC headphone as we call it, is shown to provide more than 10 dB attenuation for ultra-broadband noise - up to 6000 Hz - inside the ears in a complex sound field. The bandwidth of the controllable noise significantly exceeds the results from the state-of-the-art system, which is below 1000 Hz. The proposed method leads to the next generation of personal hearing protection system and can open up a whole new area of sound control research

Users Perceptions of Headphones and Earbuds in Norway and Brazil: An Empirical Study Based on a Kahoot Quiz

Abstract. Headphones and earbuds are seemingly more popular than ever with the wide availability of smartphones and music streaming services. Such personal audio systems are also essential for many blind and visually impaired computer users that relies on text-to-speech. Few published studies address the users’ perceptions of such personal audio output devices. However, past research shows that negative perceptions may lead to device abandonment. General-purpose equipment may therefore be more successful than special purpose assistive technologies for marginalized groups. We therefore set out to gain insight into how users generally perceive headphones and earbuds, and we wanted to base our study in two different cultural contexts. A questionnaire built on a Kahoot quiz was developed involving 12 questions related to headphones and earbuds. A total of 100 participants were recruited in Norway and Brazil. The results show that intuitiveness is the most valued feature of these devices and cost was not. Brazilians expressed skepticism regarding the use of headphones while walking and when travelling on public transport, while Norwegians expressed that headphones were safe to use in such situations. Our experiences showed that Kahoot is a promising platform for conducting such experiments, as it may appear more engaging than regular questionnaires. Moreover, they are relatively easy to set up and allow response times to be measuredacceptedVersio

Noise cancelling headphones & the neoliberal subject

Active noise cancelling (ANC) headphones grant an individual the ability to define and create personal sonic borders in real time. While this promise offers individuals a form of sonic escapism, I suggest that the technology is cloaked in neoliberal cultural values which promote individualized thinking, capital interest attained through increased focus, control of both the consumer and their sonic environment, and a Euro-centric perception of rationality and knowledge formation (J. H. Clarke et al., 2007; Gane, 2008; Houghton, 2019; Lazzarato, 2009). The technology dissolves opportunities for embodied sonic connection to land, community, and nonhuman agents which are strengthened through attentive and unmediated listening practices (Classen, 1999; Feld, 2012; Gross, 2014; Robinson, 2020; Simpson, 2011). Through a case study of Bose’s 700 NC and Apple’s Airpods Pro noise-cancelling headphones, this thesis works to uncover the ways in which the technology reproduces neoliberal ideologies utilizing CDA (Amoussue & Allagbe, 2018; Fairclough, 2001; Van Dijk, 2003) to consider how both companies advertise their noise-cancelling headphones and prioritize the neoliberal subject. Additionally, a collection of soundwalks are performed to compare the promises offered by the marketing campaigns through autoethnographic research (Behrendt, 2018; Sterne, 2003; Westerkamp, 2006). To juxtapose these neoliberal values and to offer moments for decolonial perspectives, this thesis addresses Indigenous, specifically Anishinaabe, literature on listening and sonic dimensions to consider the ways in which unmediated listening may offer moments of embodied knowledge which emerge from and through critical self-reflexivity, an awareness of an individual’s listening positionality, and a perspective on spatial intersubjectivity