GB2439766A

GB2439766A - Active noise cancellation with separate wirelessly linked units

Info

Publication number: GB2439766A
Application number: GB0613439A
Authority: GB
Inventors: Daniel Peter Somers
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-07-06
Filing date: 2006-07-06
Publication date: 2008-01-09
Also published as: GB0613439D0

Abstract

Apparatus for producing an effective personal quiet zone Q using active noise cancellation comprises two separate units; the first unit 1 containing at least one microphone (3, figure 1) for detecting noise N and a wireless transmitter (6, figure 1) for transmitting a radio frequency signal representative of the detected noise to the second unit 2 containing a wireless receiver (3, figure 4), a digital signal processor, one or more speakers (11, figure 4) and an additional microphone (13, figure 4). In use, the second unit regenerates the detected noise out of phase with the noise arriving at the quiet zone and the additional microphone provides feedback on the effectiveness of the cancellation. A securing means 28 may be provided for securing the second unit. The first unit may be attached to a wall or ceiling via adhesive means such as suckers (16, figure 1). Embodiments in which the digital signal processor is contained in the first unit or in a third dedicated unit are also disclosed.

Description

ADAPTABLE PERSONAL NOISE CANCELLATION DEVICE

The present invention relates to a mobile noise cancellation device particularly suitable for aiding sleeping.

Background to the Invention

With more and more people living in close proximity to each other, the issue of noise disturbances from neighbours is a serious problem, particularly situations such as loud music being played late at night which can disturb sleeping, diminishing health as well as peaceful enjoyment and quality of life. It is also the case that more and more people are living next to airports and roads are getting busier, but there are practical limitations as to the amount of unwanted noise which a building's walls and windows can stop. The current method adopted by people facing these situations is to wear earplugs or headphones, but these are unpleasant to wear (particularly at night), not particularly effective, and potentially with health issues such as infection, damage to the ear or getting stuck in the ear canal.

Active Noise Cancellation (ANC) is a well-known physical phenomenon, attenuating a noise by producing anti-noise', i.e. the same noise but which is 180 out of phase (also known as inverted) to cancel out the noise. Several inventions have been designed to produce a "quiet zone" without the use of headphones which broadly use the following methodology: A source microphone is used to pick up the unwanted noise and then using a Digital Signal Processor (DSP) and various algorithms, the noise signal is inverted and send it to speakers in the quiet zone. This quiet zone is sometimes controlled by the use of monitoring microphones which provide feedback to the DSP to maximise phasing, and therefore the attenuation effect, of the anti-noise.

However this applicant will show that these are unsuitable for a sleep-aiding device, addressing different problems to the main ones needing solutions: US patent no. 5,987,144 discloses A Personal Active Noise Cancellation Method and Device Having Invariant Impulse Response. This consists of a fixed arrangement of source microphones (referred to as a "sensor means"), anti-noise producing speakers (referred to as "source") and monitoring microphones (referred to as "sensors") built within a specified fixed casing (referred to as the "acoustic structure"). This casing, which is acoustically opaque save for an acoustically transparent grille covering the front, serves to keep the space around the speakers and monitoring microphones constant ("invariant"), which means that in the case where it is deployed in the headrest of an aircraft or car seat (the preferred embodiment in the patent), the performance is unchanged by movements of the person's head, thereby allowing for calibration (or more specifically pre-calibration) between the speakers and monitoring microphones which negates the need for additional electronics to perform this in real-time. This patent argues that it is an improvement of various preceding patents in the

same field for solving this problem, i.e.:

Firstly, US patent no. 5,133,017 which uses a fixed array of monitoring microphones in rings to obtain a mean signal of many monitoring inputs so that if movements of the individual's head (or hair) should block or diminish one monitoring microphone's capability, the system will still be able to function and provide a cancelling sound; the applicants of 5,987,144 argue that this is unnecessarily complex and that their solution is simpler and more effective in overcoming this problem.

Secondly (and less relevant to this application), US patent no 4,977,600 which uses a fixed arrangement of microphones and speakers, employs a pre-determined synchronous (i.e. harmonic) signal to cancel e.g. the noise of the engine in a car or aircraft; the applicants of 5,987,144 argue that this doesn't solve the problems of attenuating real-time noises.

(Note that there is another invention, US patent no 5,559,893 which discloses a method for reducing acoustic feedback in a noise-reducing system, but whilst it in the same field, and noted for completeness, the problem solved is not one which overlaps with this invention, particularly because solving feedback is not relevant when the source microphone is outside the quiet zone).

In summary:

US patent no 4,977,600 deals only with synchronous sounds: This is good for a monotonous, whirring engine but not suitable for noisy neighbours talking, shouting or playing loud music, nor overhead planes, cars or other asynchronous sounds.

US patent no 5,133,017 provides a method of improving the attenuation of a personal quiet zone by an array of source microphones, which in theory produces improvements where the individual's head or hair could block one of the microphones, although in practice is complex and only applies to a seated individual.

US patent no 5,987,144 provides an acoustic structure and arrangement which provides an improved and simplified solution to US patent no 5,133,017 by the use of a specified acoustic structure.

US patent no 5,559,893 discloses a system for reducing feedback where the source microphone is within the quiet zone and as this applicant shall show later on, is not relevant to this invention.

All of these patents are concerned with producing a quiet zone by using apparatus specifically designed to be fixed into or onto a seat, whether in an aircraft, car, workplace etc. None of these patents address the fundamental problems of producing a system suitable for assisting sleeping, i.e. a) Having an adaptable system which can be deployed with any bed (or chair) without the impracticality or expense of building it into the furniture.

b) Identify and remove specifically the source(s) of unwanted sound from an unpredictable direction so that desired sounds (e.g. an alarm clock, car-alann, or desired speech or music) can still be heard.

c) Deal with dynamic sounds effectively (e.g. loud unwanted music, noisy traffic etc.).

Of all the other inventions, US patent number no 5,987,144 is the most relevant.

However it doesn't address the major point a) above, and whilst it does deal with points b) and c) by having a source microphone outside the quiet zone, this source microphone is not designed to be mobile and therefore cannot be placed close to the source of the unwanted noise or noises (which may come from different directions at different times) and therefore would not be as effective as a mobile source microphone which can be placed.

Summary of the Invention

The present invention provides an adaptable personal noise cancellation device as defined in claim I of the set of claims following the present description of the invention. Optional and/or preferred features of the device are specified in the other claims of the set of claims.

The device of the invention has at least one or more of the following advantages: (i) it is adaptable to fit on any furniture and in particular a bed; (ii) it can isolate and attenuate a specific nuisance noise or noises coming from any unpredictable and changing direction. (iii) it is adaptable to any room layout without any inconvenient or dangerous trailing wires. (iv) it is relatively cheap to make, employing well-known, readily available components. Other advantages and benefits might be apparent to the reader.

Embodiments of the invention are now described with reference to the accompanying diagrammatic drawings in which:-Figure 1 shows the "NoiseSeeker" unit in perspective Figure 2 shows the "NoiseSeeker" unit in perspective with cut-away section Figure 3 shows the "NoiseBuster" unit in perspective Figure 4 shows the "NoiseBuster" unit in perspective with cut-away section Figure 5 shows a diagrammatic representation of the working of the invention Figure 6 shows a typical deployment of the invention, in this case a bed

Description of the drawings:

Figures 1 and 2 The "NoiseSeeker" unit 1 (or units) is a small device containing a directional source microphone 3 connected to a digital filter 4, a Radio Frequency (RF) wireless transmitter 5 and an aerial 6. It may be mains-powered and has a mains socket 14 but is primarily powered by a rechargeable battery 15. This socket can also be used for recharging the battery in situ. It has suckers 16 with which to affix itself to walls, windows and ceilings. It is contained in a sturdy case 17. It may have some status LEDs and a test button 18. The electronics are mounted on a Printed Circuit Board (PCB) 26.

Figures 3 and 4 The "NoiseBuster" unit 2 (or units) is a device containing a speaker (or speakers) 11 and a monitoring microphone 13. It has an aerial 7, a RF wireless receiver 8, and the main processing electronics, the Digital Signal Processor (DSP) 9, which is turn is connected to an amplifier 10 connected to the speaker 11, and separately a digital filter 12 connected to the monitoring microphone 13.

I

It has an adjustable clamp 19 with which to attach itself to the headboard of a bed or other supporting structure and an adjustable arm 28 so as to be able to manoeuvre the speakers and microphone close to the ears of the sleeper. It may be mains-powered and has a mains socket 20 but contains a rechargeable battery 21. This socket can also be used for recharging the battery in situ. It is contained in a sturdy case 22. It has various LED displays to inform of battery status, signal strength etc. 23. It contains other electronics 24 for ancillary functions such as sleep' mode, i.e. monitoring a lack of loud noise at the NoiseSeeker to turn the NoiseBuster on standby to conserve power, and a paging device 25 to locate the remote units in case they get lost. The electronics are mounted on a PCB 27.

Figure 5 The NoiseSeeker unit 1 is placed with the microphone 3 as close as practically possible to the unwanted source noise N. The digital filter 4 converts the analogue signal to a manageable digital signal and then it is transmitted via the transmitter 5 and then the aerial. This signal, S, is detected by the aerial 7 and receiver 8 on the NoiseBuster unit 2, whereby it is analysed by the DSP 9 and the signal inverted. This inverted signal is passed to an amplifier 10 and then to the speaker to become the noise cancelling sound A. The monitoring microphone 13 on the NoiseBuster unit measures the noise within the proposed quiet zone Q, and via a digital filter 12, feeds back to the DSP which analyses the phasing and amplitude of the signal from the monitoring microphone, with reference to the unwanted source noise. This feedback loop enables the DSP to optimise the delay and the amplitude of the signal A (which will vary depending on the distance of the NoiseSeeker from the Noisel3uster) so that after a few seconds of working the unwanted source noise N will be optimally reduced in the quiet zone. Notwithstanding this, a test-button on the NoiseBuster (18 on Figures 1 & 2) would enable the DSP to self-calibrate for delay and amplitude by emitting a recognised test signal. The parameters of the calibration would be stored in a memory chip on the PCB 9a to facilitate the real-time processing. There are many DSP programs available which could be employed here: One manufacturer is NCT Group Inc. of Westport USA.

Figure 6 The NoiseSeeker unit 1 is placed as close as practically possible to the unwanted noise N in this case stuck against a wall from which the noise is emanating. The NoiseBuster unit 2 is mounted on the headboard of the bed and the adjustable ann 28 is adjusted so that the face of the unit (containing the microphone and speaker) is close to the individual's ears and produces a quiet zone Q which in local to the individual's ears.

These figures show a preferred embodiment of the invention. Other embodiments would be (a) having two or more NoiseBuster units, (b) having two or more NoiseSeeker units (c) having a combination of both multiple unit types (some minor would be needed to have separate transmission channels for each NoiseSeeker unit), (d) having an extendable boom for the source microphone (appropriately padded to avoid injury) which would enable the quiet zone to be nearer to the individual's ears, and thus more effective particularly at higher frequencies, (e) having the NoiseBuster mounted within a specially adapted pillow (f) having different fixings for the units to accommodate different situations, e.g. sticky pads or Velcro-type material to attach the NoiseBuster to the headrest of a chair, (g) a third unit type namely a base-station' which contained the DSP and had a transmitter and a receiver to wirelessly connect with the NoiseSeeker(s) and NoiseBuster(s) to reduce the processing necessity and power consumption within the NoiseBuster unit, albeit at additional complexity and expense, (h) that the monitoring microphones are separate and worn in a head-band around the head to improve the attenuation, (i) a normal PC with speakers is used to run the DSP software and effectively become the NoiseBuster with a wireless arrangement as described, (j) the recording of known sounds and patterns (using the well-known technique of fuzzy logic) in the NoiseBuster to automatically produce anti-noise from recordings as opposed to real-time simulation.

It is important to note that the effectiveness of this invention depends upon (i) the proximity of the speakers 11 and microphone 13 to the individual's ears, and also (ii) the source microphone 3 to the unwanted noise.

The first point (i) is because it is very hard to produce synchronised anti-sound for noise with small wavelengths, as matching areas of compression with areas of rarefaction becomes increasingly difficult, particularly as the quiet zone gets larger. If the speakers are e.g. 20cm away from the ears, then the performance for attenuating sound of wavelengths 40cm or less (i.e. frequencies of approximately 1kHz or greater) will be poorer. Whilst humans can hear sounds from about 20Hz to 20kHz, higher frequencies become attenuated more easily through walls and if the invention is used as prescribed, it will have a significant effect on the unwanted noise.

The second point (ii) is because other sounds will be wanted (alarm-clock, doorbell, car-alarm etc.) so the source microphone needs to isolate the specific unwanted sound.

Also the DSP needs time to produce the correct anti-noise and whilst electromagnetic waves travel over one million times faster than sound waves, the DSP processing speed has limitations if the source is too near the quiet zone.

Claims

CLAIMS: We claim the following: I. Apparatus and method for producing

an effective personal quiet-zone, especially designed for sleeping persons using active noise cancellation, the apparatus comprising of two separate units; the first unit, the "NoiseSeeker", comprising of a device containing (a) a microphone, (b) a radio-frequency wireless transmitter and aerial, (c) suitable connecting electronics, (d) a source of electric power (such as a rechargeable battery) and/or a connection to such a source and/or to mains electricity and (e) having adhesion means such as suckers on the outside with which to attach itself to surfaces such as ceilings, walls and windows; the second unit, the "NoiseBuster", comprising of a device containing (f) a loudspeaker, (g) a microphone, (h) a digital signal processor with electronic memory, (i) a radio-frequency wireless receiver and aerial, (j) an amplifier and suitable connecting electronics, (k) a source of electric power (such as a rechargeable battery) and/or a connection to such a source and/or mains electricity and containing a rechargeable battery and on the outside (j) a securing device, which is optionally adjustable, such as an adjustable clamp on the end of an adjustable arm, the method being that the NoiseSeeker is positioned near to a region of unwanted noise using the adhesion means (e.g., suckers) such that the mounted microphone is as close to the region of unwanted noise as possible whilst the NoiseBuster is positioned by use of the aforementioned securing device (e.g., a clamp and arm) to nearby furniture or other sturdy objects (such as a bed headboard, for instance) so that the face of the unit containing the mounted speakers and microphone is adjacent to the position of ears of the said individual (for example the sleeper on the bed) or as close as reasonably possible, and the NoiseSeeker picks up the unwanted sound via its microphone and transmits it wirelessly via the transmitter and aerial to the NoiseBuster's aerial and receiver wherein it is processed by the digital signal processor into a cancelling noise signal and propagated via the speaker at the correct timing and amplitude to optimise the attenuation of the unwanted noise within the aforementioned quiet zone, whilst the monitoring microphone in the NoiseBuster provides feedback in real-time to the digital signal processor to correct/optimise the timing and amplitude to maximise the attenuation of the noise in the locality of the individual.

2. The apparatus and method of claim 1 wherein there are more than one NoiseSeeker units.

3. The apparatus and method of claim 1 or of claim 2 wherein there are more than one NoiseBuster units.

4. The apparatus and method of claims I to 3 wherein there are more than one speakers and/or microphones on the NoiseBuster unit(s).

5. The apparatus and method of claims 1 to 4 wherein there is an extendable microphone boom on the NoiseBuster unit(s) to position close to the individual's ears.

6. The apparatus and method of claims 1 to 5 wherein the NoiseBuster unit(s) is mounted in a suitable mounting inside a pillow, i.e. with the speakers and microphone facing upwards towards the sleeper's head, but with a suitable covering which is acoustically transparent, and optionally yet padded for comfort.

7. The apparatus and method of claims I to 6 wherein the NoiseBuster and NoiseSeeker unit(s) have the same or different fixings selected from the aforementioned securing device and adhesion means for the units to accommodate different situations, e.g. sticky pads, hooks or Velcro-type material to attach the units to e.g. the headrest of a chair.

8. The apparatus and method of claims I to 7 wherein there is a third unit type namely a base-station' which contains the DSP and had a transmitter and a receiver to wirelessly connect with the NoiseSeeker(s) and NoiseBuster(s) to reduce the processing necessity and power consumption within the NoiseBuster unit.

9. The apparatus and method of claims I to 8 wherein the NoiseSeeker unit contains the DSP instead of the NoiseBuster.

10. The apparatus and method of claims I to 9 wherein there is a third unit type namely a base-station' which contains the DSP and has a transmitter and a receiver to wirelessly connect with the NoiseSeeker(s) and NoiseBuster(s) to reduce the processing necessity and power consumption within the NoiseBuster unit.

11. The apparatus and method of claims 1 to 10 wherein the monitoring microphones are separate from the NoiseBuster and adapted to be worn in a head-band means around the head to improve the attenuation by being close to the ears of the said sleeper.

12. The apparatus and method of claims 1 to 11 wherein a regular PC with speakers and a microphone is used to run the DSP software and effectively become the NoiseBuster.

13. The apparatus and method of claims I to 12 wherein known sounds and patterns of sounds are recorded within any of the units to automatically produce anti-noise from recordings as opposed to real-time simulation.

14. The apparatus and method of claims I to 13 whereby a test signal from the NoiseBuster is used to calibrate the NoiseSeeker unit.

15. The apparatus and method of claims I to 13 which does not need electronic memory of any kind, and purely relies or real-time feedback conection by the monitoring microphones.

16. The apparatus and method of claims I to 15 where the apparatus are all battery-powered (or any combination of some battery powered and others mains-powered).

17. The apparatus and method of claims 1 to 16 where the wireless technology is infra-red or microwave, or some other suitable frequency of electromagnetic waves. a