Patent Application
20070160223
Not Applicable
Not Applicable
Not Applicable
Noise canceling headphones have proven to be a popular device for travelers, office workers and others who wish a reprieve from the distraction of unwanted background noise or who wish to hear with enhanced clarity the details of a particular audio source while in the presence of background noise that would otherwise detract from or mask the desired audio.
Traditional noise canceling headphones use a combination of active and passive noise reduction techniques. Passive noise cancellation techniques are used first to attenuate the noise that reaches the ear, and active noise cancellation techniques are then used to introduce noise of a type that will cancel the ambient noise and thereby minimize the net sound that ultimately reaches the ear.
Passive noise reduction is achieved by the shape and sound absorbing characteristics of the earpiece cups. Large cups that cover the ear completely are more effective, and more cumbersome, than smaller ear cups. Cups filled with sound absorbing material, such as gel, aids in reducing the sound levels that reach the ear and in turn relax the requirements on the active noise canceling electronics and transducers.
Active noise cancellation can be achieved in a number of ways and to degrees of effectiveness. But most approaches have basic similarities. A microphone within close proximity to the ear, such as within a headphone ear cup, detects audio signals within the audible spectrum (signal amplitudes and frequencies that can be detected by the human ear). This detected audio signal close to the ear, or the error signal, is used in a feedback loop. Electronics condition the error signal and produce a copy that has the same amplitude at each tone (i.e. same spectrum), but shifts the phase of the error signal by 180 degrees. This equal (in amplitude) and opposite (in phase) correction signal is then fed back to the listening environment via the speaker transducer in the headphone. When the correction signal is passed to the speaker the analog electrical signal is converted to mechanical motion which produces sound that is exactly equal and opposite to the sound detected at nearly the same instant by the built in microphone. The result of propagating the correction sound in the presence of the ambient detected noise is that the two sounds interfere and cancel, and the noise level detected by the listener is noticeably reduced from that which would heard in the absence of active noise cancellation. The servo loop bandwidth, temporal response, frequency response and other characteristic parameters are chosen to optimize the active noise canceling effect taking into account the technical performance of the passive noise cancellation sub system, and the anticipated noise characteristics to be encountered.
A drawback to the current noise canceling headphones is that they are typically stand alone products that house their own power supply, noise cancellation electronics, microphones and headphones. As a result the units are expensive and cumbersome.
An improvement to the current state of the art could be realized by an invention that takes advantage of some of the intrinsic features of a personal computer. For example desktop computers and laptops have power supplies that produce DC voltages that could be used to power the noise canceling headphones and thereby eliminate need for a battery pack.
Personal computers also often have integral microphones that may be used to enhance the noise canceling headphones. And naturally personal computers have processing, analog to digital conversion, and digital to analog conversion capabilities that may be used to enhance if not completely implement the noise canceling signal conditioning and correction signal generation. Finally, the USB connector is an elegant connection interface to pass power and signals between the personal computer and the headphone assembly that may or may not be employed. If it is employed, interesting extensions of the invention are envisioned, such as the inclusion of a digital music player, or simply digital storage on the USB connector fob.
An invention is described for a personal noise canceling system that consists of noise canceling headphones, a noise cancellation electronics module and a personal computing device. One embodiment of the invention places the noise canceling electronics module in a USB connector fob, which serves as a personal computing device, and also acts as the connection interface between the headphones and a complementary computing device. Another embodiment places the noise canceling electronics module within a decoupled personal computing device where built in audio electronics, software, firmware and power source may be leveraged for implementation of signal conditioning and processing in support of noise cancellation. It is envisioned that desirable audio signals may be injected into the noise cancellation system from a variety of sources, including but not limited to, the USB connector fob (such as digital music audio), a complementary computing device (such as DVD sound track) or an external audio source (such as airline audio channel).
There are many embodiments that can be envisioned to effectively implement the invention. Several are described herein in detail, but it will be appreciated by those skilled in the art that there are many variations on the fundamental configuration that are within the spirit and scope of this invention.
Noise Cancellation Module Integral to Personal Computing Device; Headphone to Personal Computing Device via USB Connector Fob
The preferred embodiment, shown in Figure One, consists of a Personal Computing Device, referred to herein as the PCD (e.g. desktop, laptop, mobile phone) and a Noise Canceling Headphone assembly, referred to herein as the NCH, that connects to the PCD. The connection between the PCD and the NCH is a cable terminated either directly within the PCD, or via a Connector Fob referred to herein as CF, such as a USB connector fob for example. All software, audio electronics, computing electronics, signal conditioning electronics and other devices, electronics and software necessary to implement to function of noise cancellation are herein described as components of the Noise Cancellation Module, or NCM (The NCM is a functional description, and may physically exist in one device or among devices).
A small microphone resides in each of the NCH ear cups. Noise signals are detected by the microphones integral to the ear cup and passed to the CF. Here the noise reduction module resident within the CF conditions the signal to be equal in amplitude and opposite in phase when played back through the headphone speakers. The corrected signal is passed to the NCH, where the signal is converted to sound by the speaker transducers and mixed with the resident ambient noise. The ambient noise is cancelled by the correction signal converted to sound by the NCH speakers. After cancellation, the residual noise is detected and again passed back to the cancellation electronics and the process repeats in a closed loop servo fashion to sustain maximum noise suppression in real time and in the presence of changing background noise amplitude and frequencies.
In this embodiment, the NCM resides on the PCD to reduce the requirements on noise canceling electronics external to the PCD. In the preferred configuration, the error signal is detected by microphones in the ear cup and passed through the USB CF to the PCD's internal audio electronics. Here the signal is either processed with analog electronics, or is converted to a digital format via the PCD's analog to digital converter and processed digitally. After processing, the analog correction signal (in the case of a digital domain process the signal would be converted to analog via the PCD's digital to analog converter) is passed back to the headphones to drive the headphone speakers and cancel the ambient noise, thereby achieve a reduction in unwanted background noise.
Desired audible signals may be superimposed and enjoyed in the relative absence of background noise. Desirable audio signals may originate from the PCD. Examples are; traditional software application sounds (e.g. beeps, chimes, etc.), Voice over IP (VOIP) phone conversations, or may be entertaining in nature such as music from a CD, stored digital formats such as .WAV or MP3, or may be the soundtrack to a DVD movie and so on. Alternatively, the audio source may be external to the PCD, such as an MP3 player, a cell phone, an external CD player or an airline audio source.
Noise Cancellation Module Integral to Personal Computing Device; Headphone to Personal Computing Device via Traditional Audio Connectors.
In another embodiment, shown in Figure Two, the NCH connects to the PCD via traditional audio jacks instead of a USB type connection.
Noise Cancellation Module Integral to USB Connector Fob
In another embodiment, shown in Figure Three, the NCM and associated noise canceling electronics and software (or firmware) reside within the CF. Power is supplied from the PCD to the noise canceling electronics within the CF.
Noise Cancellation Module and Digital Music Player Integral to USB Connector Fob
In another embodiment, shown in Figure Four, the NCM and a digital music player reside within the CF. Power is supplied from the PCD to the noise canceling electronics within the CF. In this configuration, digital music may be stored and retrieved from the USB CF, and desired audio content may be superimposed on the cancellation signals to provide an enhancement listening experience. Whether the CF is connected or disconnected from the PCD, operation of either noise cancellation or music generation, or a combination of the two may be employed. While disconnected from the PCD, battery power enables continued operation.
Noise Cancellation Module Integral to PCD and Digital Music Player Integral to USB Connector Fob
In another embodiment, shown in Figure Five, the NCM resides on the PCD and a digital music player reside within the CF. Power is supplied from the PCD to the digital music player within the CF. In this configuration, digital music may be stored and retrieved from the USB CF, and desired audio content may be superimposed on the cancellation signals to provide an enhancement listening experience. When the CF is disconnected from the PCD, operation of music generation is enabled by CF battery power.
Those skilled in the art will recognize that there are many more combinations of the NCH, NCM, PCD and CF that can be employed.
