The present disclosure relates to a noise reduction device, a noise reduction system or a sound field controlling method in a predetermined space. The present disclosure relates to, for example, a noise reduction device, a noise reduction system, or a sound field controlling method that is used inside an enclosed structure disposed in a movable vehicle such as an aircraft or a railway vehicle.
A movable vehicle such as noisy aircraft or vehicle sometimes provides services such as music stream for passengers seated in seats. When an aircraft or railroad vehicle travels at high speed, various types of noise are generated at different places in the vehicle due to vibration caused by the engine or motor that drives the vehicle, air colliding with the structure of the vehicle, and other such phenomena. How this noise travels to each seat, the volume (amplitude) of the noise at each seat, and how long the noise takes to reach each seat (phase) differ depending on where the seat is located.
JP-A-1998-171468 discloses a method in which speakers are arranged and positioned in view of the point where noise is to be reduced (also called as “silence center” or “control point”), thereby enhancing reduction of a random noise.
Japanese Patent No. 2642857 discloses an acoustic crosstalk control device capable of sound amplification independently in each of adjacent seats. The acoustic crosstalk control device performs addition processing to the regular music information for a passenger at the first position so as to cancel out a crosstalk sound from the second position in the adjacent seat, thereby suppressing the crosstalk sound.
The noise reduction device, the noise reduction system or the sound field control system of the present disclosure is effective for effectively generating a sound field in the target space while obtaining the noise reduction effect.
The noise reduction device of the present disclosure includes a sound receiver, a sound source input, a sound adjuster, a control sound generator, a controller, and a sound output. The sound receiver receives a first sound signal acquired from a microphone. The sound source input receives an input of a second sound signal from a sound source. The sound adjuster changes an intensity of the second sound signal relative to an intensity of the first sound signal. The control sound generator generates a third sound signal that reduces the first sound signal. The controller controls a change of the intensity of the second sound signal and controls the generation of the third sound signal. The sound output outputs the third sound signal and outputs the second sound signal to the speaker at the intensity changed by the sound adjuster.
The noise reduction system of the present disclosure includes the noise reduction device, one or more microphones for acquiring noise, and one or more speakers for outputting the second sound signal and the third sound signal.
The sound field controlling method of the present disclosure is a sound field controlling method for controlling a sound in a target space. The method includes receiving a first sound signal acquired from a microphone, receiving from a sound source a second sound signal different from the first sound signal, changing an intensity of the second sound signal relative to an intensity of the first sound signal, generating a third sound signal that reduces the first sound signal, and outputting the third sound signal to a speaker, and outputting to the speaker the second sound signal whose intensity has been changed.
Hereinafter, embodiments will be described in detail, with reference to the drawings when appropriate. Any explanations deemed unnecessary may be omitted. For example, detailed descriptions of well-known aspects or duplicate descriptions of substantially identical components may be omitted from this disclosure. This is to avoid unnecessary redundant description in the following and to facilitate understanding by those skilled in the art.
It is to be noted that the attached drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and they are not intended to limit the claimed subject matter.
Hereinafter, the noise reduction device or the noise reduction system according to the present embodiment will be described by way of an example where the device is mounted on an aircraft 100.
First, an acoustic environment in the aircraft 100 that requires the installation of the noise reduction device will be described using
As shown in
The engines 102a and 102b act as, for example, external noise sources NS1a and NS1b relative to rows of seats 103a, 103b, and 103c respectively located in a seating cabin A (for example, first class), a seating cabin B (for example, business class), and a seating cabin C (for example, economy class) in the aircraft. In addition, the noise (wind roar) of air colliding with the air flow at the tip and side faces of the body of the aircraft and the wings 101a and 101b when the aircraft 100 travels at high speed in the airspace acts as a noise source NS1c and adversely affects the provision of information services and the like in the aircraft 100.
Furthermore, an air conditioning system (not shown) equipped with pressurization, ventilation, and temperature control functions is installed in the aircraft 100 in order to clean, maintain, and circulate air inside the aircraft. The sound from the air conditioning system is also a noise source in addition to the noise sources NS1a, NS1b, and NS1c, as described later.
The seating cabin 100a is partitioned into a seating cabin A and a seating cabin B by walls 100w. Seating rows 103a and 103b are located in the seating cabin A and the seating cabin B, respectively.
The acoustic environment in the entire seating cabin 100a includes, as external noise sources, the noise sources NS1a and NS1b generated by the engines 102a and 102b, and wind roars (noise source NS1c) at the tip and side face of the aircraft body. Furthermore, there are the noise sources NS2a to NS2e generated by the air conditioning system and other components, as internal noise sources.
Assume that one seat 105 in the seating cabin A is affected by the noise from the noise sources. The seat 105 is affected by noise from noise sources NS1a to NS1c generated by the sound of airflow and the engines 102a and 102b (see
In the first class shown by the seating cabin A or the like in
The noise reduction system 300 is a feedforward noise reduction system, and includes a noise microphone 320, a noise controller 330, a control sound speaker 340, and an error microphone 350, as shown in
The noise microphone 320 is a microphone that detects noise emitted from the noise source 310, converts the detected noise information into an electrical signal, and outputs the electrical signal.
The error microphone 350 is a microphone that detects a residual sound (error sound) obtained by superimposing the noise emitted from the noise source 310 and the control sound emitted from the control sound speaker 340, converts the error sound into an electrical signal, and outputs it. The control sound is a sound signal generated so as to cancel out the noise.
The noise controller 330 includes a processor and a memory including circuitry such as a DSP (Digital Signal Processor) or a CPU. As shown in
The adaptive filter 332 is a circuit that generates a control sound signal that reduces noise. The adaptive filter 332 is configured by multistage taps, and is a FIR (Finite Impulse Response) filter that can freely set the filter coefficient of each tap. The coefficient updating unit 333 is provided by a predetermined algorithm executed by a processor. The coefficient updating unit 333 obtains a control sound from the error microphone 350 via the A/D converter 335, in addition to the noise input from the noise microphone 320. Then, the coefficient updating unit 333 adjusts each filter coefficient of the adaptive filter 332 so as to minimize the error sound. In other words, the adaptive filter 332 and the coefficient updating unit 333 generate a control sound signal having a phase opposite to the noise from the noise source 310 at a control point where the error microphone 350 is installed. The generated control sound signal is output to the control sound speaker 340 via the D/A converter 334.
The transfer function correction unit 336 is a multistage tap FIR filter that represents a transfer function within the range of the transfer path. That is, the transfer function correction unit 336 expresses the transfer function between the output of the adaptive filter 332 generating a control sound through the D/A converter 334 and the control sound speaker 340, and the generated control sound reaching the coefficient updating unit 333 through the error microphone 350 and the A/D converter 335.
The A/D converter 331 is provided for each noise microphone 320 and includes a circuit that converts the noise signal from the noise microphone 320 from analog to digital. The A/D converter 331 outputs to the coefficient updating unit 333 through the adaptive filter 332 and the transfer function correction unit 336. With signals passing the transfer function correction unit 336, it is possible for the output of the adaptive filter 332 to reflect transfer characteristics including echo cancellation such as reflection or delay to the error sound signal that has been A/D converted and is input to the coefficient updating unit 333, thereby calculating accurate filter coefficients.
The control sound speaker 340 is a speaker that converts a control sound signal received from the D/A converter 334 into a sound wave and outputs the sound wave. The control sound speaker 340 emits a control sound that reduces the noise reaching the vicinity of the ear 301b of the user 301.
The error microphone 350 detects the noise-reduced sound as an error, and provides feedback on the operation result of the noise reduction system 300. As a result, even when the noise environment or the like changes, noise can always be minimized at the user's ear position.
In the noise reduction system 300 of the basic configuration shown in
The shell 110a is surrounded on all sides by the front wall 110aa, rear wall 110ab, side wall 110ac, and side wall 110ad. The side wall 110ad is formed with an opening for the passenger to enter and exit the shell 110a. Also, the shell 110a has a rack 110ae in front of the seat 105 at a position surrounded by the front wall 110aa and both side walls 110ac and 110ad. The rack 110ae is used, for example, as a desk.
The seat 105 has a backrest (not shown), a seating part 105a on which the user 401 is seated, a headrest 105c and armrests 105d and 105e. Further, a noise controller 330 (corresponding to the noise controller 330 in
In the acoustic environment in the seating cabin A in an aircraft, there are noise sources such as engines 102a, 102b mounted on the aircraft, an air conditioner disposed inside the seating cabin, and other noise sources. Around the seat 105, the noise emitted from each noise source reaches the outer peripheral portion of the shell 110a. In the seat 105, as shown in
If there are various noise sources, such as aircraft noise, and no major noise path can be identified, a plurality of omnidirectional noise microphones may be placed in or near the target space for noise reduction, formed by the shell 110a (control space).
As shown in
Therefore, noise can be effectively reduced in the low to high frequency band even when there are many noise sources or noise coming from various directions as in the seating cabin of the aircraft 100.
The present disclosure further provides a noise reduction device, a noise reduction system or a sound field controlling method that adopts a controlling method not causing sound leakage to the next seat in the above mentioned environment, thereby enabling the user to receive music service from the speaker in the target space without using headphones.
The noise reduction device or the noise reduction system according to Embodiment 1 will be described using
1-1. Configuration
The noise controller 530 includes an A/D converter 531 (an example of a sound receiver), an A/D converter 535, an adaptive filter 532 (an example of a control sound generator), a coefficient updating unit 533, a D/A converter 534 (an example of a sound output), and a transfer function correction unit 536, which correspond to the A/D converters 331 and 335, the adaptive filter 332, the coefficient updating unit 333, the D/A converter 334, and the transfer function correction unit 336 shown in
The noise controller 530 additionally includes a sound source input 537 (an example of a sound source input), a mixer 538, a sound source transmission correction unit 539, and a buffer amplifier 53A (an example of a sound adjuster).
The sound source input 537 acquires a sound source signal. The sound source signal may be received from an external device or may be stored in advance in a memory. The sound source signal may be, for example, music distribution from the system management apparatus 104, sounds and voices from AVOD services such as movies and music enjoyed by passengers at each seat 105, sound effects and sounds for sleeping and wake-up, BGM, and in-flight broadcasts by crew members.
The mixer 538 mixes the sound source signal from the sound source input 537 with the control sound that cancels out the noise, and outputs the mixed sound through the control sound speaker 540. With the configuration, music service can be provided to passengers without using headphones through the speakers within seats.
The sound source transmission correction unit 539 is functionally the same as the transfer function correction unit 536 for noise, and expresses the transfer characteristics (transfer function and echo cancellation) for the sound source signal.
The buffer amplifier 53A buffers the inputted sound source signal, and adjusts the sound pressure level and the frequency characteristics of the sound source signal according to the characteristics of the noise signal.
1-2. Operations
The A/D converter 531 of the noise controller 530 acquires a noise signal from the noise microphone 520 (S1011). The sound source input 537 acquires a sound source signal (S1012). The buffer amplifier 53A changes the intensity of the sound source signal relative to the intensity of the noise signal (S1013). An example of changing the intensity of the sound source signal relative to the intensity of the noise signal will be described with reference to
The sound pressure level of the sound source signal (Fm) and the sound pressure level of the noise signal (Fnc) to be adjusted are preferably measured or estimated by calculation near the ear of a user in an adjacent seat. However, adjusting the sound pressure levels acquired at noise microphones and error microphones disposed inside the shell structure 110, 110′, for example, can also provide an effect in which the sound source signal is reproduced and output through the speakers while sound is prevented from leaking to the outside of the seat 105.
The mixer 538 may adjust the sound pressure level of the sound source signal in place of the buffer amplifier 53A. In this case, the mixer 538 mixes the sound source signal (Fm) acquired and selected from the buffer amplifier 53A so as to be smaller than the sound pressure level of the noise signal (Fnc).
As described above, the buffer amplifier 53A actively adjusts the acoustic characteristic value, such as frequency spectrum or sound pressure level, of the sound source signal by the control of the coefficient updating unit 533.
The adaptive filter 532 generates a control sound signal that reduces the noise signal (S1014). The mixer 538 mixes the sound source signal whose sound pressure level has been adjusted with the generated control sound signal, and outputs the mixed signal to the control sound speaker 540 via the D/A converter 534 (S1015). The process of steps S1011 to S1015 is repeated (S1016) unless a condition for the end of the operation occurs such as a shut-down of the noise restriction system.
Human voices tend to be perceived even under noise. Therefore, when the sound source signal is a human voice, outputting the sound source signal (Fmc) with a further reduced sound pressure level is effective for sound leakage prevention.
When the sound source signal is reproduced, the intensity of the sound source signal relative to the intensity of the noise signal may be adjusted by delaying the reproduction of the sound source in accordance with sound pressure fluctuation due to the time periodicity of the noise signal. If some of the frequency components of the controlled sound source signal (Fmc) shown in
When the sound source input 537 receives a predetermined sound for broadcasting, for example, an announcement by a crew member, the sound pressure level of the predetermined sound may not be changed. This is because all users need to hear in-flight broadcasting etc., for which no sound leakage need to be prevented.
1-3. Features, etc.
The noise controller 530 (noise reduction device), the noise reduction system 500 or the sound field controlling method according to Embodiment 1 adjusts the sound pressure level or the frequency characteristic of the sound source signal according to the noise frequency spectrum in the target space for sound field control in a seat. Therefore, while noise reduction effect can be obtained, it is possible to prevent sound leakage to an adjacent seat. Thus, the user in the seat 105 can enjoy music appreciation and individual sound service through the speakers at the seat 105 without using headphones. Furthermore, the noise transmitted from the engines of the aircraft and the wind roar is reduced, thereby realizing a comfortable space in the aircraft.
A noise reduction system 1100 according to Embodiment 2 will be described using the block diagram of
The description of the same functions as those of the configuration of the noise reduction system 500 shown in
Unlike the noise reduction system 500, the noise reduction system 1100 includes a sound source speaker 1141 separately from the control sound speaker 1140. The sound source speaker 1141 reproduces and outputs a sound source signal. The noise reduction system 1100 further includes a D/A converter 1134a (an example of sound output) that outputs the sound source signal to the sound source speaker 1141. The noise reduction system 1100 does not have a mixer. The buffer amplifier 113A outputs to the sound source speaker 1141 the sound source signal (Fmc) whose sound pressure level has been adjusted as shown in
In the noise reduction system 1100, the buffer amplifier 113A outputs the sound source signal to the sound source speaker 1141 via the D/A converter 1134a. The sound source speaker 1141 outputs a reproduced sound from the sound source, while the control sound speaker 1140 outputs a control sound.
The control sound speaker 1140 may be designed to be suitable for a low frequency sound in order to output a control sound that reduces noise. Therefore, with the configuration in which the sound source speaker 1141 suitable for the sound of the sound source signal including high frequency is additionally provided, it is possible for the user to hear the sound source signal with a good sound quality. Furthermore, since the position of the sound source speaker 1141 is not limited like the control sound speaker 1140, the arrangement of speakers can be flexible and therefore, a freedom of the design for the target space of sound field control can be greater.
<1>
The system management apparatus 104 is a computer device, for example, a server device that manages the system inside the aircraft.
The noise reduction systems 500a, 500b have a similar configuration and function to Embodiment 1 or Embodiment 2, but have an additional configuration and function as follows.
The noise reduction system 500a includes a processor 500ap including circuitry such as a DSP and a CPU, and executes the processing according to a program to implement the function of the sound source signal controller 501. The sound source signal controller 501 adjusts the sound pressure level of the sound source signal with the buffer amplifier 53A (or the mixer 538 shown in
The sound leakage is detected based on the sound from noise microphones installed in the adjacent shell structure 110. As the noise microphone 520 of the noise reduction system 500b, for example, noise microphones 520g and 520d′ are selected, which are disposed near the adjacent shell structure 110 as shown in
As shown in
Although
<2>
The arrangement, the number, the operation, and the operation type of the speakers and the microphones are not limited to those of the above examples.
The noise reduction device (noise controller) may be installed at a place other than the inside of the backrest of the seat 105. For example, the noise reduction device may be installed under a seating part of the seat 105, or in a space on the side of or behind the seat 105.
<3>
The noise controllers 530 and 1130 (noise reduction devices) may be installed not only in the seating cabin in an aircraft but also, for example, in a pilot seat of an aircraft or the like in order to reduce noise in the pilot seat. Or, the noise reduction device may be installed in other vehicles, such as a helicopter, a train, a bus, etc. Furthermore, the noise reduction device may be installed in a building where noise is generated, such as a building nearby a construction site, in a club with live music etc.
<4>
In the above-described embodiments, some or all of the processing for functional blocks may be executed by a program. Further, some or all of the processing for the functional blocks in the above-described embodiments may be executed by a processer in a computer. The program for executing this processing may be stored in a storage device such as a hard disk or a ROM and run by being read out by the ROM or a RAM.
In the above embodiments, the processor described as a DSP or CPU may be replaced with a processor that is configured as a dedicated electronic circuit designed to implement predetermined functions. The processor may be made up of one or a plurality of processors.
The processes of the sound field controlling method shown in
<5>
In the present disclosure, an apparatus or a system includes a set of a plurality of components (apparatus, modules (parts), and the like). It does not matter whether all the components are in a single housing or not. A “system” may refer to both a plurality of devices located in separate housings and connected to each other via a network, and one device in which a plurality of modules are located in one housing.
In understanding the scope of the present disclosure, the term “configured” as used herein to describe a component, section, or a part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function.
In understanding the scope of the present disclosure, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms “including,” “having,” and their derivatives. Also, the terms “part,” “section,” “portion,” “member,” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts.
While only selected exemplary embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the exemplary embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
This application claims benefit to U.S. provisional application No. 62/734,260 filed on Sep. 21, 2018. The entire disclosure of U.S. provisional application 62/734,260 is hereby incorporated herein by reference.
Number | Date | Country | |
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62734260 | Sep 2018 | US |