Patent Application
20060039569
Not applicable
Not applicable
This invention relates to a method of reducing acoustic energy (sound) emanating from a toilet and from its human user.
When a toilet is used by a human there is a loud and sometimes embarrassing noise made by the human excrements (solid, liquid or gaseous) when these are ejected from the body. Noise is also made when these excrements contact components of the toilet, such as the toilet bowl or the water surface inside the toilet. Often these sounds are amplified by resonating within the cavity enclosed on one side by the toilet bowl and on the other side by the person's exposed posterior, or even by the room in which the toilet is located. Additionally, noise is made by the toilet's flushing action, as well as by the refilling of the water tank in the toilet. Finally, noise is made by closing of the toilet seat, often when it falls onto the toilet bowl generating a large amplitude sound. All these above mentioned noises are a source of annoyance and embarrassment to persons.
Many proposals have been made to reduce various sources of noise in the toilet. Many of these proposals have focused on reducing noise emanating from flushing or from toilet use through the employment of mechanical devices to deflect human waste, muffling devices, methods of circulating water inside the toilet during flushing, and other similar contraptions. Many of these approaches are impractical to implement, particularly in the case where an already installed toilet cannot be replaced due to reasons of cost, complexity or efficacy of noise level reduction.
In the previously mentioned proposals, the method for reducing noise is passive. A passive system's primary benefit is derived from attenuating the noise energy, or in reducing the amount of noise energy generated in the first place by the physical event (such as water rushing through a valve). Due to many of these advances, modem toilets have significantly reduced the noise made by flushing and refilling of the water tank. One significant disadvantage of these techniques is that they are effective in reducing noise if the whole toilet and water supply is upgraded to this less noisy approach incorporating such techniques. This is impractical or too costly in a significant number of locations where toilets have been previously installed.
None of the general techniques mentioned above are effective in reducing human generated noises in the toilet, often the largest source of embarrassment; hence these solutions do not solve the central problem of toilet noise abatement. As an illustration of this point, it is common in Japanese toilet users to employ a special electrical button that generates a flushing sound from an electronic recording of such flushing sound (rather than from water flushing inside the toilet) in order to mask other human generated sounds. In this scenario, the toilet user wishes to emanate a loud flushing sound, thereby increasing the overall toilet noise level, rather than suppressing such sound.
An alternative approach to the problem of toilet noise reduction is to employ the concept of acoustic noise destructive interference. In this method, a sound signal of equal and opposite phase to that of the unwanted noise is generated (typically through the use of an acoustic speaker similar to ones used in audio entertainment equipment.) When combined in the air (or other physical medium), the result is a net noise level that is attenuated due to the summing of the original noise signal with the canceling signal of opposite phase and equal magnitude. This approach works well so long as the requirements of equal magnitude and opposite phase are met. However, these requirements are difficult to meet in a real-world implementation of such a system.
One inventor, Tsutsui (Japanese patent No. JP403181996A “Low flushing sound toilet stool”, Tsutsui et al), proposes to use this noise canceling method by generating a pre-recorded flushing sound (with approximately opposite phase and equal magnitude) through a speaker embedded in the toilet. The effect of generating this sound, when done at precisely the correct time, is to reduce the overall sound level due to a toilet flushing. This approach has several key problems that reduce its efficacy. First, the flushing sound which had been pre-recorded at the toilet factory varies significantly from the actual sound that emanates from the toilet flushing in an actual installation at a toilet site in use. This variation is due to the fact that the acoustics in the factory are necessarily different from a real installation (where each installation is acoustically unique), and the circumstances for flushing also vary from use to use (is the human user is sitting on the toilet or not, when flushing? The contents of the toilet bowl vary when flushing, etc.) Secondly, this approach requires a precise synchronization from the electronic payback of the recorded sound with the flushing action (which can vary significantly due to actuator aging, water pressure, etc.) Thirdly, this approach is only practical, if it was effective in the first place, with newly built toilets and is not practicable with existing installation of toilets. Finally, this approach only works for previously known sounds, namely, the flushing sound (and as has been already demonstrated, such sound tends to vary significantly over each use.) Another inventor, Suzuki (Japanese patent No. JP405132986A “Noise attenuating method for toilet bowl”, Suzuki et al), proposes to overcome some of the limitations of Tsutsui by updating the recorded flushing sound every time the toilet is flushed. Suzuki relies on a pre-recorded toilet flushing sound. This approach does enhance the fidelity of the recorded sound to that of the characteristics of each particular toilet installation, as compared to Tsutsui. However, the other problems mentioned in the Tsutsui patent remain. Suzuki mentions in his patent's Claim #1 Paragraph #5 that it is difficult to attenuate the flushing sound after the flushing sound has started, thereby prescribing the use of the pre-recorded flushing sound cancellation method.
Both Suzuki and Tsutsui affirm the utility of applying active noise cancellation techniques to attenuate noise emanating from toilets. However, they both fall short of an effective and useful method for doing so.
The present invention described below solves the problem to which Suzuki alludes, and thus applies the solution not only to flushing sounds, but to all other sounds produced inside the toilet.
Accordingly, several objects and advantages of this invention are that toilet noise is reduced, regardless of its source. The invention reduces noise energy, and therefore the perceived loudness of that noise, emanating from the flushing action, from the water tank filling, from human generated noises (solid, liquid, and gaseous), and from ancillary toilet noise sources (such as the falling of the toilet seat onto the toilet bowl). The previously mentioned techniques are limited in their effectiveness to specific noise sources, are thus are not effective, or are simply inoperable, against the broader spectrum of noise sources emanating from within the toilet and its user. Additionally, the character of the noise sources to be canceled by the invention includes both transient and steady-state elements. It is generally easier to attenuate steady-state noise sources, as they are, by definition, repetitive (and thus one can use historical parameters of the steady-state components of the noise to generate a cancellation signal at the present time). As for canceling the transient components of the noise, a real-time adaptive approach is required for efficacy. The invention describes this approach.
Other objects and advantages of this invention are that the apparatus embodying the invention may be installed and utilized onto existing toilets, without the need to replace the toilet or to modify any plumbing. The apparatus embodying the invention is relatively small as compared to the typical dimensions of the western style toilet bowl, and thus is not difficult to retrofit onto existing toilets. The previously mentioned techniques typically require a significant (and costly) modification to the toilet, including often the complete replacement of the toilet and related plumbing accessories.
Another object and advantage of the invention is to reduce the noise energy emanating from the toilet regardless of the noise's characteristics, which may vary with time, with temperature, with the level of humidity, with the level of water pressure, with the amount and type of waste in the toilet, with the acoustic characteristics of the rest of the room where the toilet is located, and with the physical characteristics and position (relative to the toilet) of the human currently using the toilet, and other acoustic variations. The previously mentioned techniques related to electronic noise cancellation are ineffective against human made noises, and do not accommodate changing acoustic properties of the toilet, its user and the surroundings.
The invention consists of the application of adaptive and active electronic noise cancellation techniques in the toilet bowl. One or more acoustic speakers (electrical to acoustical energy transducers) are located within the toilet bowl, in close proximity to the majority of noise sources to be attenuated. The speaker generates acoustic waves that interfere destructively with the noise to be attenuated. The net sound energy, resulting from the interference of the speaker with the noise source, is attenuated as compared to the original noise source. The speaker is electrically stimulated from an electronic circuit containing a digital signal processing circuit, one or more digital-to-analog converters and one or more analog-to-digital converters. The digital signal processor processes the sound energy received from one or more microphones (acoustic to electrical energy transducers) in order to compute the appropriate output signal to be sent to the speaker via the digital-to-analog converter(s) and amplifier(s). At least one microphone is located in close proximity to the noise source to be attenuated.
A preferred embodiment of the physical placement of the major components of the invention is illustrated in
A preferred embodiment of the present invention's logical block diagram of the major components is illustrated in
A preferred embodiment of the present invention's digital signal processing circuit computation is shown in
In an alternative embodiment of the invention, only a single acoustic microphone, namely acoustic reference microphone 155, may be utilized. In this embodiment, the resulting performance of the invention, as measured by the amount of audible noise cancellation of the noise source is somewhat reduced as compared to the use of at least one additional microphone, namely acoustic error microphone 180. Correspondingly, the computations performed by digital signal processing circuit 240 in a single-microphone embodiment is less complex than in two or more microphone embodiments.
In an alternative embodiment of the invention, a multiplicity of acoustic speakers may be utilized to improve the noise cancellation performance of the invention.
In an alternative embodiment of the invention, electrical power may be provided to the invention from sources other than AC power (typical wall outlet). For example, a battery may be used. This battery may be of the primary type whereby it is not rechargeable and must be replaced when it has been drained of its capacity. Alternatively, such a battery may be of the rechargeable type. A multiplicity of battery recharging methods may be utilized to provide power to the invention. Some of these methods include the use of light-to-electrical converters (similar to solar cells), AC power (in this case the battery continues to provide electrical power to the invention even if AC power is temporarily unavailable), mechanical-to-electrical power derived from the movement of water during the flushing of the toilet or the refilling of the toilet's tank.
In an alternative embodiment of the invention, invention enclosure 145 containing invention printed circuit board 160 may be located physically outside toilet 100, or in another location within toilet 100. The location of reference microphone 155 and primary acoustic speaker 150 must be located within the confines of toilet 100, but may be moved from the location shown in the preferred embodiment of the invention to another location. An alternative location may be on the inner side of toilet 100, embedded at the time of manufacturing toilet 100 within the toilet structure (such as in a cavity in the plastic or ceramic make-up of toilet 100), or inside back portion of toilet 115. In the case where toilet 100 is designed and manufactured to accommodate the invention internally, it is possible to use electrical power cables and electrical power sources that may be used in toilet 100 for other functions unrelated to the invention (such as automatic flushers, toilet seat or water warmers, and a variety of other toilet functions). The location of error microphone 180 may be separated from invention electrical cable 165 and moved to its own separate location, either physically separated from toilet 100 with a separate cable (or wireless connection), or embedded within toilet 100 or back portion of toilet 115 in a manner that is as far away physically as practical from acoustic noise source 200. It is important that any components of the invention that are placed within toilet 100 be protected in an enclosure that is waterproof as well as resilient to cleaning from brushes or such implements as might be used to clean toilet 100.
How Acoustic Noise Cancellation Works
Acoustic noise cancellation works by the interference of the acoustic noise energy with the speaker acoustic energy. If the speaker generates the same acoustic signal as the noise, but with opposite phase and equal magnitude, then these two signals interfere destructively, resulting in a net energy that is close to zero (hence, silence). Some of the key factors contributing to a less-than-perfect acoustic noise cancellation are the distance of the speaker from the noise source, the time delay that the electronic system requires in order to generate an opposite phase acoustic signal, and the fidelity of the electro-acoustic components (microphones, speakers, resonant chamber made up of the toilet system) including their time-changing properties. In a real-world implementation of an acoustic noise canceling system, all three of these factors interact and affect how the designer might trade-off their respective implementation.
Below, each of these three major critical performance parameters is examined as well as how the invention copes with these issues.
Distance of the speaker to the noise source. The wavelength of sound at 600 Hz is approximately 1.9 feet (at room temperature and sea level conditions). In order for the noise cancellation to be effective (i.e., greater than a 10 dB reduction in noise level), it is important that the distance between the two sources of noise be less than 0.2 wavelengths (Hansen “Understanding active noise cancellation”, Spon Press). Therefore, in order for the 600 Hz noise component to be sufficiently attenuated for a human to perceive such attenuation, a maximum distance of 4.5 inches is required. The bulk of the noise energy of interest to the invention lies in the lower frequency spectrum of human hearing; hence a 600 Hz upper limit is reasonable for purposes of calculating desired maximum distances. The invention places the primary acoustic speaker within such a distance inside the toilet. A related concern is the location of the reference acoustic microphone. The location of this microphone is also critical in efficacy of the noise canceling system performance. The invention also locates this microphone close to the noise source. If an error microphone is used, then it is equally critical that the error microphone be located relatively far from the noise source, namely, at least one wavelength away. The invention places the error microphone far from the inside of toilet bowl by attaching it at some distance from the invention enclosure on the invention electrical cable. Finally, it is critical to note that the acoustic properties of the inside of the toilet bowl change with each use, as the physical properties (size, shape, temperature, humidity, and a multiplicity of such factors) of the acoustic chamber also change. Therefore the location of the acoustic elements (reference microphone and primary speaker) within the toilet ensures that the proper electro-acoustic conditions are in place for the invention's efficacy. Placing these elements outside the toilet leads to significantly lesser noise cancellation, particularly at the higher frequencies.
Time delay to generate the opposite phase acoustic signal. The active noise cancellation approach of the invention uses an adaptive technique. Unlike the Suzuki and Tsutsui patents, the invention does not store a previously recorded digital replica of the noise to be cancelled (in the other patents' cases, they store the flushing sound only, ignoring the other human-generated sounds). The invention relies on the real-time computation of the acoustic signals detected by the reference and error microphones in order to generate the canceling signal of the primary speaker. Therefore, the total time delay from when the noise source originally produces a particular sound energy, until the primary speaker's acoustic corresponding energy interferes in the physical medium (most of the interference of the two energy sources occurs within the air inside the toilet bowl) is a very critical parameter in determining the efficacy of the invention. The time delay is measured against the period of the frequency of the noise spectral component to be cancelled. Hence, a particular time delay results in worse performance (due to a greater phase shift) at the higher frequencies than at the lower frequencies. The first major contributing time delay is that of the sound propagation from the noise source to the reference microphone, and subsequently from the primary speaker to the noise source where the in-air interference can ideally take place. The speed of sound is approximately 331 meters/sec. Assuming that the distance from the noise source to the primary microphone is 4.5 inches, the sound takes approximately 0.34 milliseconds to travel such distance. This time delay is equivalent to 0.2 times the period of a 600 Hz noise component (or almost 75 degrees of phase shift). By taking into account the time delay of the sound emanating from the primary speaker (which is almost identical to that of the noise-to-microphone delay), it is reasonable then to double the overall delay to 0.68 milliseconds. Other sources of delay are the phase shifts inherent in the construction of the microphone and of the speaker. The preferred embodiment of the invention uses a MEMS microphone construction and an Ultrasonic-response speaker (both of which exhibit a fast response time and thus lower delay). The reason for these preferred choices are to minimize the time delays contributed by these two elements. The internal circuitry of the invention also contributes some delays to the overall system. The contributions to delay of the low pass filters, analog to digital converters, digital to analog converters, and amplifiers are generally negligible. The last contributor to system delay is the computation performed within the digital signal processing circuit. That delay is a function of the complexity of the computation, the speed of the digital signal processing circuit, as well as the inherent algorithmic delays inherent in the computation (for example, the inherent phase shift due to a digital filter implementation in the digital signal processing circuit, such phase shift being due to the nature of the filter characteristics rather than the complexity of its computation). The invention mitigates the signal processing delay by using a modern digital signal processing circuit capable of high speed operation (on the order of 100 MHz basic digital clock rate).
Fidelity of acoustic components and their time-changing properties. The acoustic characteristics of the main elements that make-up the noise canceling system have a significant impact on the efficacy of the invention. The major factors affecting the acoustic characteristics of the system include:
a) initial manufacturing part-to-part tolerance of the electro-acoustic components (microphones, speakers)
b) changes of electro-acoustic components' parameters due to aging
c) installation (location and orientation) of invention within the toilet as well as the location of the error microphone
d) toilet bowl and toilet seat properties (size, shape material, construction, attachment)
e) surrounding region of the toilet (size of room sound dampening or resonant characteristics)
f) external changes to the acoustic coupling (for example, water or other foreign materials on the surface of the invention enclosure)
g) temperature and humidity
h) changes to the acoustic characteristics of the toilet system that occur with each use of the invention. This includes the water level inside the toilet, foreign materials inside the toilet (level, shape, type), the human using the toilet (location, size, shape, orientation, clothing), the toilet seat (location and orientation), and the changes to the surrounding region of the toilet (such as open or closed windows, changes in the contents of the room, curtains open or closed), character of acoustic energy sources outside the toilet and their coupling to the inside of the toilet.
The invention copes with the large number and unpredictability of possible variations in the acoustic environment with the use of (a) an adaptive computation of the digital signal of primary acoustic speaker, (b) an error microphone, and (c) a closed-loop computation as shown in
From the description above, a number of advantages of the present invention become evident:
a) The volume of undesired noise generated within the region of the toilet is actively reduced, including both flushing noise as well as noise emanating from a human user of the toilet.
b) The invention may be added to existing toilets, without the need for significant replacements of toilets, plumbing, or other structural changes. Additionally, the invention may also be embedded into the design and manufacture of a new model toilet for new installations, rather than a retrofit of a toilet.
c) The invention works all the time, it does not require a triggering event (such as an input from the flushing system) to activate it.
d) The invention is small enough to be located in an effective region with respect to proximity to noise sources, but does not interfere with the normal operation of a toilet.
e) The invention adapts automatically and often to changes in the acoustic environment of the toilet and its surroundings and users, hence maximizing its efficacy in a greater spectrum of operating and installation situations.
This application claims the benefit of provisional patent application Ser. No. 60/602,967, filed 2004 Aug. 19 by the present inventor.
| Number | Date | Country | |
|---|---|---|---|
| 60602967 | Aug 2004 | US |
