Audio noise cancelling circuit
One of the favorite benefits of headphones is the ability to help focus. Headphones on. World Out. On your commute, in the office, at the gym - nearly everywhere humans use headphones to help them focus or get away. Step 2: Inside the headphone is a microphone that picks up those sounds and sends them through the noise canceling process. Step 3: A noise cancellation circuitry inverts the wave to create a new waveform and sends it to the headphones speaker.
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Active noise cancelling
Effective date : Year of fee payment : 4. An electronic device may be coupled to an accessory such as a pair of earphones. The earphones may have noise cancellation features that may be implemented using noise cancellation circuitry in the earphones or in the electronic device. The earphones may have ear presence sensor structures that determine whether speakers in the earphones are present at the ears of a user.
In one suitable embodiment, control circuitry in the earphones may be used to adjust noise cancellation circuitry in the earphones based on information from the ear presence sensor structures. For example, the control circuitry may deactivate noise cancellation circuitry in response to receiving information from the ear presence sensor structures indicating that the earphones have been removed from a user's ears. In another suitable embodiment, control circuitry in the electronic device may adjust noise cancellation circuitry in the electronic device based on information from the ear presence sensor structures.
Accessories such as earphones are often used with media players, cellular telephones, and other electronic devices. Some accessories have microphones that are used to form part of a noise cancellation circuit. When noise cancellation functions are active, the impact of ambient noise on audio playback can be reduced. Microphones can also be used to implement voice microphone noise cancellation. There can be difficulties associated with noise cancelling earphones. For example, a user who is using earphones to listen to audio while noise cancellation circuitry in the earphones is active may occasionally need to remove the earphones.
When doing so, the user may not be able to manually turn off noise cancellation features. Actively running noise cancellation operations in an accessory when a user is not using the accessory increases power consumption and decreases the battery life of the accessory. It would therefore be desirable to be able to provide improved ways in which to control operation of an electronic device coupled to an accessory such as noise cancelling earphones.
An electronic device may be coupled to an accessory such as a pair of earphones having noise cancellation features. The noise cancellation features may be used to reduce the impact of ambient noise on the audio content that is played through the earphones.
The earphones may have ear presence sensor structures that determine whether or not speakers in the earphones are present at the ears of the user. Information from the ear presence sensor structures may be used to control the operation of the noise cancellation features. In one suitable embodiment, noise cancellation features may be implemented using noise cancellation circuitry in the earphones.
With this type of configuration, control circuitry in the earphones may adjust the noise cancellation circuitry in response to information from the ear presence sensor structures. For example, control circuitry in the earphones may automatically deactivate noise cancellation circuitry when information from the ear presence sensor structures indicates that the earphones have been removed from a user's ears.
When information from the ear presence sensor structures indicates that the earphones have been placed in or on the user's ears, the control circuitry in the earphones may, if desired, automatically activate the noise cancellation circuitry. In another suitable embodiment, noise cancellation features may be implemented using noise cancellation circuitry in the electronic device.
With this type of configuration, information from ear presence sensor structures may be conveyed to control circuitry in the electronic device. The control circuitry may adjust the noise cancellation circuitry in response to information received from the ear presence sensor structures. For example, control circuitry in the electronic device may automatically deactivate noise cancellation circuitry when information from the ear presence sensor structures indicates that the earphones have been removed from a user's ears.
Controlling the operation of noise cancellation circuitry based on whether or not the earphones are present at the user's ears may reduce the power consumption of a battery in the earphones or in the electronic device. The ear presence sensor structures may include switch-based sensors, accelerometer-based sensors, light-based sensors, or other suitable types of sensors.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. Electronic device accessories such as earphones may be provided with noise cancellation features. When noise cancellation features are activated, the impact of ambient noise on audio content that is played through the earphones can be reduced.
Noise cancellation features may also be used to perform voice microphone noise cancellation. Noise cancellation features may be implemented using one or more noise cancellation microphones. For example, a voice microphone in the accessory may have an associated noise cancellation microphone that picks up ambient noise in the vicinity of the voice microphone. Earphone speaker housings in an accessory may also have noise cancellation microphones.
For example, each earphone speaker housing in a headset may have an external noise cancellation microphone on an outer surface of the earphone speaker housing. In addition to the external noise cancellation microphone or instead of the external noise cancellation microphone, each earphone speaker housing may have an internal noise cancellation microphone on an interior surface of the earphone speaker housing e.
In accessories with more speakers, more noise cancellation microphones may be used. For example, additional noise cancellation microphones can be provided in earbuds that contain multiple drivers or in surround sound accessories. A surround sound accessory might, for example, have five or six speakers or more and might have a noise cancellation microphone that is adjacent to each respective speaker.
Accessories such as earphones having noise cancellation features may be provided with the ability to sense the presence of external objects. For example, an earphone accessory may be provided with sensor structures such as ear presence sensor structures that can determine whether or not the earphones i.
Information gathered by the sensor structures may be used to control the operation of noise cancellation features in the earphones. For example, control circuitry in the accessory or in the electronic device may automatically activate or deactivate noise cancellation features based on whether or not the earphones are located in or on the ears of a user.
As shown in FIG. Electronic device 10 may include a display such as display Display 14 may be a touch screen that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components or may be a display that is not touch-sensitive. Display 14 may include an array of display pixels formed from liquid crystal display LCD components, an array of electrophoretic display pixels, an array of plasma display pixels, an array of organic light-emitting diode display pixels, an array of electrowetting display pixels, or display pixels based on other display technologies.
Configurations in which display 14 includes display layers that form liquid crystal display LCD pixels may sometimes be described herein as an example.
This is, however, merely illustrative. Display 14 may include display pixels formed using any suitable type of display technology.
Display 14 may be protected using a display cover layer such as a layer of transparent glass or clear plastic. Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button such as button 16 and an opening such as opening 18 may be used to form a speaker port. Device 10 may have a housing such as housing Housing 12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal e.
Housing 12 may be formed using a unibody configuration in which some or all of housing 12 is machined or molded as a single structure or may be formed using multiple structures e. The periphery of housing 12 may, if desired, include walls. One or more openings may be formed in housing 12 to accommodate connector ports, buttons, and other components. For example, an opening may be formed in the wall of housing 12 to accommodate audio connector 24 and other connectors e.
Audio connector 24 may be a female audio connector sometimes referred to as an audio jack that has two pins contacts , three pins, four pins, or more than four pins as examples. Audio connector 24 may mate with male audio connector 22 sometimes referred to as an audio plug in accessory Accessory 20 may be a pair of earphones e. The use of a pair of earphones in system 8 is sometimes described herein as an example. Accessory 10 may be implemented using any suitable electronic equipment.
Cable 26 may contain conductive lines e. The conductive lines of cable 26 may be used to route audio signals from device 10 to speakers in earphone units Earphone units 28 which may sometimes be referred to as speakers or earphone housings may include sensor structures for determining when earphone units 28 have been placed within the ears of a user. Microphone signals may be gathered using a microphone mounted in controller unit Controller unit 30 may also have buttons that receive user input from a user of system 8.
A user may, for example, manually control the playback of media by pressing button 30 A to play media or increase audio volume, by pressing button 30 B to pause or stop media playback, and by pressing button 30 C to reverse media playback or decrease audio volume as examples. The circuitry of controller 30 may communicate with the circuitry of device 10 using the wires or other conductive paths in cable 26 e.
The paths in cable 26 may also be coupled to speaker drivers in earphones 28 , so that audio signals from device 10 may be played through the speakers in earbuds Electronic device 10 may regulate the volume of sound produced by earbuds 28 by controlling the audio signal strength used in driving the speakers in earbuds In one suitable embodiment, sensor signals from sensor structures in earbuds 28 may be conveyed to device 10 using the conductive paths of cable With this type of configuration, electronic device 10 may process the sensor signals and take suitable action based on a determination of whether or not earphones 20 are located in or on a user's ears.
A schematic diagram showing illustrative components that may be used in device 10 and accessory 20 of system 8 is shown in FIG. Control circuitry 32 may include storage and processing circuitry that is configured to execute software that controls the operation of device Control circuitry 32 may be implemented using one or more integrated circuits such as microprocessors, application specific integrated circuits, memory, and other storage and processing circuitry.
Control circuitry 32 may, if desired, include noise cancellation circuitry and other audio processing circuitry Input-output circuitry 34 may include components for receiving input from external equipment and for supplying output.
For example, input-output circuitry 34 may include user interface components for providing a user of device 10 with output and for gathering input from a user. Radio-frequency transceiver circuitry in the wireless circuitry may be used to handle wireless signals in communications bands such as the 2.
Input-output devices 38 may include buttons such as sliding switches, push buttons, menu buttons, buttons based on dome switches, keys on a keypad or keyboard, or other switch-based structures. Input-output devices 38 may also include status indicator lights, vibrators, display touch sensors, speakers, microphones, camera sensors, ambient light sensors, proximity sensors, and other input-output structures.
Electronic device 10 may be coupled to components in accessory 20 using cables such as cable 26 of accessory Accessory 20 may include speakers such as a pair of speaker drivers 40 e. If desired, accessory 20 may include more than one driver per earbud.
For example, each earbud in accessory 20 may have a tweeter, a midrange driver, and a bass driver as an example. Speaker drivers 40 may be mounted in earbuds or other earphone housings. The use of left and right earbuds to house respective left and right speaker drivers 40 is sometimes described herein as an example.
Accessory 20 may include control circuitry such as control circuitry Control circuitry 45 may, for example, include storage and processing circuits formed from one or more integrated circuits or other circuitry. Circuitry 45 in accessory 20 may include noise cancellation circuitry and other audio processing circuitry 48 , if desired. Cables such as cable 26 may form a communications path that can be used in conveying signals between device 10 and accessory The communications path may be used to transmit audio from circuitry 32 to speaker drivers 40 during playback operations.
Noise-cancelling headphones
Effective date : Year of fee payment : 4. An electronic device may be coupled to an accessory such as a pair of earphones. The earphones may have noise cancellation features that may be implemented using noise cancellation circuitry in the earphones or in the electronic device. The earphones may have ear presence sensor structures that determine whether speakers in the earphones are present at the ears of a user.
Building Noise Canceling Headphones
Documentation Help Center Documentation. This principle has been applied successfully to a wide variety of applications, such as noise-cancelling headphones, active sound design in car interiors, and noise reduction in ventilation conduits and ventilated enclosures. In this example, we apply the principles of model-based design. First, we design the ANC without any hardware by using a simple acoustic model in our simulation. The Speedgoat is an external Real-Time target for Simulink, which allows us to execute our model in real time and observe any data of interest, such as the adaptive filter coefficients, in real time. The following figure illustrates a classic example of feedforward ANC. The noise source b n is measured with a reference microphone, and the signal present at the output of the system is monitored with an error microphone, e n. The primary path is the transfer function between the two microphones, W z is the adaptive filter computed from the last available error signal e n , and the secondary path S z is the transfer function between the ANC output and the error microphone. Also, the acoustic feedback F z from the ANC loudspeaker to the reference microphone can be estimated F' z and removed from the reference signal b n.
Analog Noise Cancelling Headphones
A stereo noise creates a huge disturbance, especially when you are listening to weak radio stations. Peaks of unwanted background noise take over the broadcast signal, making it unpleasant. The noise is always disturbing in the intervals when the music stops. Different noise filters, noise removal strategies.
Noise-Cancellation or Sound-Isolation: What’s the Difference?
Analog noise-reduction systems must be able to distinguish between "hiss", or white noise, and the source material, and then attenuate the noise. One method of noise rejection assumes that all signal levels below a pre-selected magnitude are noise, and then attenuates that noise via a voltage-controlled amplifier VCA. This double-ended encode-decode approach achieves about 9 to 10dB of improvement in signal-to-noise ratio by incorporating a high-pass compressor on the recording side and a high-pass expander during playback. Another technique senses and rejects noise by measuring the frequency content of the audio signal and then filtering all noise that occurs above the highest audio frequency. The principal key to the SSM's ability to reject noise is its ability to recognize the noise floor, whether it be the low-level hiss of an audiotape, or the higher-level noise interfering with reception of weak stations in an automobile radio. This is accomplished in a patented noise threshold detector, which operates on the principle that virtually all program material contains gaps during which the only energy present especially at frequencies in the 3-kHz to 8-kHz region is noise.
AS3415 Active Noise Cancellation
Our ENC headsets are specially designed for pilots of aircraft which generate noise at lower frequencies. Active reduction of unwanted noise is achieved by a process which amounts to cancellation of the noise by generating a signal identical in sound pressure level SPL but exactly reversed in phase to the offending noise ; the effect being a cancellation see fig. Electronic Noise Cancelling is accomplished in the following manner: A miniature microphone is placed in the ear cup next to the earphone element and as near as possible to the entrance of the ear canal. This microphone senses the noise as it enters the ear. The signal developed by the sensing microphone represents noise which has penetrated the passive attenuation barrier, and is composed of predominantly low frequencies. This signal is fed to a circuit where it is inverted in phase, amplified, and then drives an earphone creating an anti-noise signal which cancels the intruding noise.
Active noise control
Noise-cancelling headphones have become popular in consumer markets over the past few years. This has caused a little bit of confusion about the differences between sound-isolation and noise-cancellation. They're not interchangeable.
Here, we explain what ANC is and how it differs from previous noise cancelling concepts. We have already touched on the theme of noise cancellation several times on the blog. Distracting street noise, monotonous humming on transport or whirring noises from ventilation systems are already a thing of the past for users of noise-cancelling headphones. The component that technically removes noise from the audio signal is the ANC controller, which is supported by one or more microphones as sensors. Of course, the ANC controller does not detect the noise directly from its source, but at appropriate frequencies with which noise perceived by us is transmitted.
Product Status: Discontinued Final Delivery. Analog ANC solution Integrated active noise cancellation solution with integrated bypass function addressing feedforward architecture for stereo wired headsets, suitable for music, video or mobile use. Final lifetime buy order must be placed by June 30, Please contact your local sales representative for further information. View Details. Asset Publisher. General Description Analog ANC solution Integrated active noise cancellation solution with integrated bypass function addressing feedforward architecture for stereo wired headsets, suitable for music, video or mobile use.
Using your new knowledge of how sound works and with a basic understanding of circuitry and electronics, you can construct an active noise-cancelling circuit ANC! This circuit can also be attached to headphone jacks to attach it to your heaphones! The main idea behind noise-cancelling headphones involves the placement of a microphone on the exterior of the headphones, which picks up external noise. These sounds are then inverted every sign is changed i.
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