Patent Description:
Music services may be provided to passengers seated in moving objects such as noisy aircraft and vehicles. Since aircraft and railroad vehicles move at high speeds, various noises are generated in various places. Noise is generated, for example, by vibration generated from a power source engine or motor, or by collision noise between a moving object that is moving and air. The noise arrival direction, the volume (amplitude), and the noise arrival time (phase) differ depending on the seat.

PTL <NUM> discloses a method for reproducing an area of voice using a speaker array. In this method, a noise level is measured from the environmental sound, and the reproduced sound is adjusted such that at each frequency, the sound pressure of the reproduced sound reaching the reproduction line in the control line exceeds the noise level, and the sound pressure of the reproduced sound reaching the non-reproduction line in the control line does not exceed the noise level.

PTL <NUM> discloses methods and systems that are provided for adjusting a crossover frequency between a plurality of audio speakers rendering audio content. In one example, a first subset of a plurality of audio speakers may be rendering a first sub-range of a range of audio frequencies of an audio content, and a second subset of speakers of the plurality of audio speakers may be rendering a second sub-range of the range of audio frequencies. In this example, the first sub-range and the second sub-range may be substantially separated at the crossover frequency. In one case, a playback volume at which the audio content is being rendered may be adjusted. In one instance, the crossover frequency may be adjusted in response to the volume adjustment to improve the audio content rendering quality by the respective subsets of audio speakers in the plurality of audio speakers.

The present disclosure provides a voice control device and a voice control system that are effective in effectively generating a sound field in a target space where noise is generated.

A voice control device of the present disclosure is a voice control device as defined in claim <NUM>.

A voice control system of the present disclosure is a voice control system as defined in claim <NUM>.

The voice control device and voice control system of the present disclosure are effective in effectively generating a sound field in a target space where noise is generated.

Hereinafter, exemplary embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters and duplicate explanations for substantially the same configuration may be omitted. This is to avoid unnecessary redundancy of the following description and to facilitate the understanding of those skilled in the art.

The accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

A first exemplary embodiment provides a voice control device, a voice control system, and a voice control method capable of forming a sound field space in which a user can enjoy the content voice without headphones or earphones, while reducing noise in an environment where predetermined noise is generated such as an aircraft.

Hereinafter, an example of the case where the voice control system of the first exemplary embodiment is mounted on aircraft <NUM> will be described.

First, the sound environment in aircraft <NUM> will be described with reference to <FIG> and <FIG>.

As shown in <FIG>, aircraft <NUM> includes left and right wings 101a and 101b, and engines 102a and 102b mounted on wings 101a and 101b, respectively. Here, considering the sound environment of space inside aircraft <NUM>, sound emitted from engines 102a and 102b is a large noise source because it is accompanied by not only the rotating sound but also the reverberation of the air flow during flight.

Engines 102a and 102b act as external noise sources NS1a and NS1b, for example, with respect to seat rows 103a, 103b and 103c respectively installed in cabin A (for example, first class), cabin B (for example, business class) and cabin C (for example, economy class), in the aircraft. Further, the collision noise (wind noise) between the air flow and the tip portion, the side surface portion, and both wings 101a and 101b of the airframe accompanied by the movement of the airframe at high speed in the air layer acts as noise source NS1c. Therefore, the music providing service in aircraft <NUM> is adversely affected.

Further, in order to clean, maintain, and circulate the air inside the aircraft, an air conditioning system (not shown) equipped with pressurization, ventilation, and temperature control functions is mounted on aircraft <NUM>. As will be described later, the sound generated by the air conditioning system also serves as a noise source in addition to noise sources NS1a, NS1b, and NS1c.

<FIG> is a plan view showing details of the installation environment of the voice control device. <FIG> shows an enlarged view of the arrangement of seats in cabin A and a part of cabin B in <FIG>.

A cabin 100a is divided into cabins A and B by wall 100w, and cabins A and B are provided with seat rows 103a and 103b, respectively. On the other hand, as the sound environment in cabin 100a, there are noise sources NS1a and NS1b generated from engines 102a and 102b and wind noise (noise source NS1c) at the tip portion, side surface portion, and both wings of the airframe as external noise sources. Further, there are noise sources NS2a to NS2e from an air conditioning system or the like as noise sources inside cabin 100a.

For example, noise in one seat <NUM> disposed in cabin A is affected by noise from noise sources NS1a to NS1c caused by engines 102a and 102b (see <FIG>) attached to the wings outside the window and the airflow noise and noise sources NS2a to NS2e caused by the air conditioning system, in seat <NUM>.

In the first class shown in cabin A in <FIG>, each seat <NUM> is surrounded by a target space for voice control (an example of a predetermined space) that is shell structure <NUM> as shown in <FIG>. Shell structures <NUM> and <NUM> are provided with a system for reducing noise. As shown in <FIG>, noise microphones <NUM> are disposed at predetermined positions of shell structures <NUM> and <NUM>. Control sound speaker <NUM> is disposed in each seat <NUM>. In this system, a control sound signal having a phase opposite to the noise acquired from noise microphone <NUM> is generated by the noise reduction control described later, and is output from control sound speaker <NUM>. Thus, the noise in shell structures <NUM> and <NUM> is reduced.

On the other hand, inside shell structure <NUM>, audio visual equipment such as a television and a radio for enjoying movies and music, a desk for businessmen, a PC connection power supply, and the like are disposed. Seats <NUM> in first class and the like are required to provide passengers (hereinafter referred to as users) with an environment in which the users can relax and concentrate on the business.

It is conceivable to use control sound speaker <NUM> for viewing and listening to movies, music, and the like. However, in that case, the following problems arise.

The graph of <FIG> shows the frequency distributions of noise signal S1 and content voice signal S2. As shown in <FIG>, noise signal S1 has a characteristic that the sound pressure level in the low frequency range is high and the sound pressure level in the high frequency range is low. Sound leakage occurs in the frequency band in which the sound pressure level of content voice signal S2 exceeds the sound pressure level of noise signal S1. In noise signal S1, the sound pressure level is reduced to some extent by the output of the control sound for noise reduction, but the noise in the low frequency range is large. Therefore, even if noise signal S1 is reduced by the control sound, it is considered that noise signal S1 is not lower than the sound pressure level of content voice signal S2 in the low frequency band. On the other hand, noise signal S1 is lower than the sound pressure level of content voice signal S2 in the high frequency band. Therefore, even in a noisy environment, when user U listens to the content voice without headphones or earphones, sound leakage occurs in the high frequency range of the voice. In particular, as shown in <FIG>, when the target spaces for voice control are disposed next to each other, sound leaks to the adjacent aisles and seats. Such sound leakage is annoying to other users U, and hinders the operation of the aircraft.

Further, control sound speaker <NUM> is a speaker suitable for outputting a control sound that reduces noise, that is, for outputting a low frequency signal. Therefore, control sound speaker <NUM> is not particularly suitable for the output of content voice signal S2 having large high frequency signals.

In the voice control device, the voice control system, or the voice control method according to the first exemplary embodiment, the output of the sound source signal is divided according to the frequency band, and divided signals are output from two different speakers. This implements an environment in which user U can enjoy viewing the content in shell structure <NUM> without using headphones or earphones.

Hereinafter, the configuration and operation of the voice control device, the voice control system, and the voice control method will be described by providing the speaker for the high frequency range according to the first exemplary embodiment.

<FIG> shows the basic configuration of voice control system <NUM>. Voice control system <NUM> is disposed in the space of each seat. Voice control system <NUM> includes voice control device <NUM>, speaker group <NUM>, and microphones group <NUM>.

Voice control device <NUM> includes Digital Signal Processor (DSP) <NUM>, D/A converter group <NUM>, A/D converter group <NUM>, and network card (NIC) <NUM>. DSP <NUM> includes a circuit and a memory for executing voice control including noise reduction control as described later. Each D/A converter (an example of the voice output unit) of D/A converter group <NUM> is connected to each speaker. Each D/A converter converts the voice signal and the control sound signal generated by DSP <NUM> from a digital signal to an analog signal and outputs the converted signal to the speaker. Each A/D converter (an example of a sound collection signal input unit) of A/D converter group <NUM> is connected to each microphone. Each A/D converter converts the voice collected by the microphone from an analog signal to a digital signal and inputs the converted signal to DSP <NUM>. Network card <NUM> (an example of a sound source signal input unit) includes a circuit or a terminal for communicating with management device <NUM>. Network card <NUM> receives sound source data <NUM> of the content from management device <NUM>.

Speaker group <NUM> includes control sound speaker <NUM> and speaker array <NUM> shown in <FIG>. Control sound speaker <NUM> is a speaker designed to be suitable for outputting a low frequency signal. As will be described later, control sound speaker <NUM> amplifies and outputs the control sound signal output from noise reduction controller <NUM>. The control sound is a voice signal generated to offset the noise. Control sound speaker <NUM> also amplifies and outputs the low frequency signal of the sound source signal, as will be described later. Speaker array <NUM> is a speaker suitable for high-pitched sound output, and includes a plurality of speakers disposed in a row. As will be described later, speaker array <NUM> amplifies and outputs a high frequency sound signal such that the sound power is concentrated in the vicinity of a control point on the head of user U, by a wave field synthesis technique.

As shown in <FIG>, microphone group <NUM> include content voice detection microphone <NUM>, noise microphone <NUM>, and error microphone <NUM>.

Content voice detection microphone <NUM> is a microphone for detecting a content reproduction signal output in the space of shell structure <NUM>, and collects sounds around the microphone. The voice signal collected by content voice detection microphone <NUM> is input to frequency determination unit <NUM> of DSP <NUM> via corresponding A/D converter <NUM>.

Noise microphone <NUM> is a microphone for detecting the sound emitted from the noise source, and collects the sound around the microphone. The voice signal collected by noise microphone <NUM> is input to noise reduction controller <NUM> of DSP <NUM> via corresponding A/D converter <NUM>.

Error microphone <NUM> is a microphone for detecting residual sound (error sound) as a result of overlapping the sound emitted from the noise source and the control sound emitted from control sound speaker <NUM>. Error microphone <NUM> is disposed near the head of user U, which is a control point. A plurality of content voice detection microphones <NUM>, a plurality of noise microphones <NUM>, and a plurality of error microphones <NUM> may be provided.

As shown in <FIG>, the voice controller system may be connected to management device <NUM> of aircraft <NUM>. Management device <NUM> includes a processor including a control circuit such as a CPU and a memory, and includes a computer that operates according to a predetermined program. Management device <NUM> stores sound source data <NUM> of the content. Sound source data <NUM> of the content includes sound source data of the content that can be viewed by user U as desired, such as a voice of music, a movie, a television, a radio, or the like.

By executing a predetermined program, DSP <NUM> executes the functions of frequency determination unit <NUM>, band controller <NUM>, sound image controller <NUM>, and noise reduction controller <NUM> shown in <FIG>.

Frequency determination unit <NUM> determines the cutoff frequency based on the content reproduction signal and the noise signal. Specifically, frequency determination unit <NUM> acquires the content reproduction signal collected by content voice detection microphone <NUM>. The sound collection signal collected by content voice detection microphone <NUM> also includes a noise signal. The frequency determination unit acquires, for example, the frequency characteristics of the content reproduction signal as shown in <FIG>, by removing the noise signal in shell structure <NUM>, from the sound collection signal. The noise signal in shell structure <NUM> may be measured in advance and stored in a memory, when the content reproduction signal is not output from the speaker. The noise signal has frequency characteristics similar to those of noise signal S1 shown in <FIG>, that is, the lower the frequency, the higher the sound pressure level. Frequency determination unit <NUM> determines the cutoff frequency at which the sound pressure level of the content reproduction signal becomes equal to or higher than the sound pressure level of the noise signal, from the frequency characteristics of the content reproduction signal and the frequency characteristics of the noise signal acquired from content voice detection microphone <NUM>. The cutoff frequency is, for example, the frequency indicated by P1 shown in <FIG>.

The cutoff frequency changes according to changes in the sound pressure level and frequency characteristics of the content reproduction signal collected by content voice detection microphone <NUM>. Therefore, frequency determination unit <NUM> monitors such a change, and changes the cutoff frequency when the change occurs.

Frequency determination unit <NUM> may make a determination according to the number of speakers in speaker array <NUM>, at least in the initial state. Further, content voice detection microphone <NUM> may be disposed in the vicinity of control sound speaker <NUM>, and determine the cutoff frequency according to the frequency band of the low frequency signal output from control sound speaker <NUM>.

Band controller <NUM> acquires the sound source signal of the content, from sound source data <NUM>. Band controller <NUM> includes filter circuits such as a Low Pass Filter (LPF), a High Pass Filter (HPF), and a Band Pass Filter (BPF), and divides a sound source signal into two band signals, according to the cutoff frequency determined by frequency determination unit <NUM>. Specifically, band controller <NUM> acquires a high frequency signal in a frequency band equal to or higher than the cutoff frequency and a low frequency signal in a frequency band equal to or lower than the cutoff frequency, from the sound source signal. The high frequency signal is input to sound image controller <NUM>. The low frequency signal is output to control sound speaker <NUM> together with the control sound signal output from noise reduction controller <NUM>.

The frequency band equal to or higher than the cutoff frequency includes both the case where the cutoff frequency is included and the case where the cutoff frequency is not included. Similarly, the frequency band equal to or lower than the cutoff frequency includes both the case where the cutoff frequency is included and the case where the cutoff frequency is not included.

Sound image controller <NUM> performs a wave field synthesis process for controlling at least one of the phase and the sound pressure level of the acquired high frequency signal such that the sound image is localized at the control point near the head of user U. As shown in <FIG>, sound image controller <NUM> includes a plurality of wave field synthesis filters 15a, 15b,. , which are digital filters. Wave field synthesis filters 15a, 15b,. correspond to speakers 52a, 52b,. of speaker array <NUM>, respectively, and form a plurality of channels (for example, <NUM> channels). For each of wave field synthesis filters 15a, 15b,. , filter coefficients are set according to the distance between the control point near the head of user U in shell structure <NUM> and speaker array <NUM>. By convolving the filter coefficient, the output from speaker array <NUM> is controlled to concentrate the power of the high frequency sound signal output in the vicinity of the designated control point. Thus, even if the sound pressure level is reduced, user U can sufficiently hear the voice signals from speakers 52a, 52b,. of speaker array <NUM>.

Noise reduction controller <NUM> generates a control sound signal for reducing the noise signal, and outputs the control sound signal to control sound speaker <NUM> via D/A converter <NUM>. As shown in <FIG>, noise reduction controller <NUM> includes adaptive filter <NUM>, and coefficient update unit <NUM>.

Adaptive filter <NUM> is a circuit that generates a control sound signal that reduces noise. Adaptive filter <NUM> is, for example, a Finite Impulse Response (FIR) filter that is composed of multi-stage taps and can freely set the filter coefficient of each tap.

Coefficient update unit <NUM> is implemented by a predetermined algorithm (for example, Least Mean Square (LMS)) executed by the processor. Coefficient update unit <NUM> acquires the error sound from error microphone <NUM> in addition to the noise input from noise microphone <NUM>. Coefficient update unit <NUM> updates the transfer function and adjusts each filter coefficient of adaptive filter <NUM> such that this error sound is minimized. Thus, a control sound signal having a phase opposite to the noise from the noise source is generated at the control point near the installation position of error microphone <NUM>. The generated control sound signal is output to control sound speaker <NUM> via D/A converter together with the low frequency signal of the sound source signal of the content described above.

<FIG> and <FIG> show an arrangement example of the microphone and the speaker according to the first exemplary embodiment. In <FIG> and <FIG>, the upper view is a plan view, and the lower view is an elevation view corresponding to the plan view. User U is lying in shell structure <NUM>.

In the example shown in <FIG>, control sound speaker <NUM> is disposed at a control point near the head of user U. Since control sound speaker <NUM> outputs a control sound that reduces noise, it is desirable that control sound speaker <NUM> is disposed near the control point. On the other hand, speaker array <NUM> is disposed at a position away from the control point (for example, the wall in front of the foot side of user U). As described above, the sound image of the voice signal output from speaker array <NUM> is localized in the vicinity of the control point, by the wave field synthesis process by sound image controller <NUM>. Therefore, even if the output of each speaker of speaker array <NUM> is small, it is possible to provide user U with a sufficiently audible volume. Further, since speaker array <NUM> can reduce the sound output, the risk of sound leakage can be reduced. Content voice detection microphone <NUM> is disposed above and close to the control point in shell structure <NUM>.

The arrangement of speaker array <NUM> is not limited to the arrangement shown in <FIG>. For example, as shown in <FIG>, speaker array <NUM> may be disposed near the control point. In <FIG>, the longitudinal direction of speaker array <NUM> is disposed vertically with respect to the floor surface of seat shell structure <NUM>. Such an arrangement has an effect of facilitating the wave field synthesis of the voice signal output from each speaker configuring speaker array <NUM> such that the sound emitted by speaker array <NUM> has a directivity so as to be prevented from leaking to the outside of the shell beyond the edge of shell structure <NUM>.

Although <FIG> shows an example in which speaker array <NUM> is disposed such that longitudinal direction is perpendicular to the floor surface, it is not always necessary to arrange speaker array <NUM> strictly perpendicular to the floor surface. The same effect can be obtained even if the longitudinal direction of speaker array <NUM> is deviated from the vertical direction and slanted.

Further, when the direction of the edge of shell structure <NUM> is, for example, the horizontal direction or the vertical direction, speaker array <NUM> may be disposed such that the longitudinal direction of speaker array <NUM> is perpendicular to the edge direction of shell structure <NUM>. Further, the intervals between the individual speakers of speaker array <NUM> may be irregular or uniform. When the surface of shell structure <NUM> is a curved structure, the speakers may be disposed side by side along the surface of the curved structure such that the distance between the individual speakers is substantially uniform.

That is, when the speakers configuring speaker array <NUM> are disposed such that the vertical distances from the floor surface to the installation locations are all different, the effects described above can be obtained.

Further, in the arrangement example of the microphone and the speaker according to the first exemplary embodiment, content voice detection microphone <NUM> is provided independently, but it is not always necessary to provide a dedicated microphone for detecting the content reproduction signal. Even if each noise microphone and error microphone installed in shell structure <NUM> share functions and are used as content voice detection microphone <NUM>, a certain effect can be obtained.

The operation of voice control device <NUM> will be mainly described with reference to <FIG>. User U requests the distribution of the sound source data by operating the remote controller or the touch panel installed in seat <NUM>. Thus, the sound source signal is received (S101). Further, the sound collection signal collected by content voice detection microphone <NUM> is received (S102). The noise reduction control by noise reduction controller <NUM> is executed in parallel.

Frequency determination unit <NUM> acquires a content reproduction signal from the sound collection signal collected by content voice detection microphone <NUM>, and determines the cutoff frequency, based on the content reproduction signal and the noise signal (S103). Band controller <NUM> acquires a high frequency signal in a frequency band equal to or higher than the cutoff frequency and a low frequency signal in a frequency band equal to or lower than the cutoff frequency, from the sound source signal (S104).

The high frequency signal is subjected to a wave field synthesis process by sound image controller <NUM> (S105). The high frequency signal subjected to the wave field synthesis process is output to speaker array <NUM> (S106). On the other hand, the low frequency signal is output to control sound speaker <NUM> together with the control sound signal generated by noise reduction controller <NUM> (S107).

When an end condition such as stop of the transmission of the sound source signal occurs, the process ends (S108). On the other hand, when the end condition does not occur, frequency determination unit <NUM> continues to monitor changes in the sound pressure level and frequency characteristics of the content reproduction signal collected by content voice detection microphone <NUM>. Frequency determination unit <NUM> repeats the operations of steps S102 to S108, according to the change.

By the above operation, the sound pressure level of the content reproduction signal can be controlled so as not to exceed the sound pressure level of the noise signal. Therefore, user U can enjoy the sound without headphones or earphones, while preventing the sound from leaking from shell structure <NUM> to the outside.

<FIG> shows a configuration of voice control system <NUM> according to a modification example of the first exemplary embodiment. In the same modification example, tweeter <NUM> is provided instead of speaker array <NUM>, and sound image controller <NUM> is not provided. Tweeter <NUM> is a speaker suitable for high-pitched sound output. The high frequency signal divided by band controller <NUM> is output to tweeter <NUM> via D/A converter <NUM>. As shown in <FIG>, which is a diagram similar to <FIG> and <FIG>, tweeter <NUM> is disposed on the left and right in the vicinity of the control point. Thus, user U can sufficiently hear the output sound even if the output is small, and can reduce the risk of sound leakage.

In <FIG>, tweeter <NUM> is disposed below shell structure <NUM> in accordance with the state in which user U is lying in shell structure <NUM>. On the other hand, when it is assumed that user U hears the sound in a sitting posture, tweeter <NUM> may be disposed above shell structure <NUM> as shown in <FIG>.

In voice control system <NUM>, voice control device <NUM>, or the voice control method according to the first exemplary embodiment, the cutoff frequency is determined based on the content reproduction signal output from the speaker and the noise signal, the sound source signal of the content is divided into a high frequency signal in a frequency band equal to or higher than the cutoff frequency and a low frequency signal in a frequency band equal to or lower than the cutoff frequency, the low frequency signal is output to control sound speaker <NUM> that outputs a control sound signal for noise reduction, and the high frequency signal is output to speaker array <NUM>.

The high frequency signal that causes sound leakage to the outside of shell structure <NUM> is subjected to the wave field synthesis process and output from speaker array <NUM>. Thus, it is possible to prevent sound leakage while providing a sound having a sufficient sound pressure level with a small output level to the control point near the head of user U, for the high frequency signal. On the other hand, for the low frequency signal that is relatively unsuitable for speaker array <NUM>, control sound speaker <NUM> that is provided for noise reduction and is suitable for the low frequency signal is used. Thus, while preventing sound leakage, it is possible to complement the sounds in different frequency bands with each other by control sound speaker <NUM> and speaker array <NUM>, and it becomes possible to reproduce the sound of content in a wide band near the head of user U. Therefore, user U can view the content without using headphones or earphones.

In addition, by monitoring the changing cutoff frequency, the cutoff frequency is changed according to changes in the content and noise signal, and the voice can be controlled such that the sound pressure level of the high frequency signal does not exceed the sound pressure level of the noise signal. Therefore, sound leakage can be prevented more reliably.

Further, since the noise reduction operation can be executed in parallel, the sound of the content can be reproduced while reducing the noise.

Voice control system <NUM> according to a second exemplary embodiment will be described with reference to <FIG>. The same configurations and functions as those in the first exemplary embodiment are designated by the same reference numerals, and the description thereof will be omitted.

Voice control system <NUM> according to the second exemplary embodiment is different from voice control system <NUM> according to the first exemplary embodiment in that it does not have noise reduction controller <NUM>. The low frequency signal of the sound source signal acquired by band controller <NUM> is output to low frequency speaker <NUM> via the D/A converter. Low frequency speaker <NUM> may be a speaker having the same configuration and function as control sound speaker <NUM>.

As described above, voice control system <NUM> according to the second exemplary embodiment has the same effect as that of the first exemplary embodiment except for the noise reduction effect even when the noise reduction process is not executed. That is, while preventing sound leakage, it is possible to complement the sounds in different frequency bands with each other by low frequency speaker <NUM> and speaker array <NUM>, and it becomes possible to reproduce the sound of content in a wide band near the head of user U. User U can view the content without using headphones or earphones.

In voice control system <NUM> according the the claimed invention, tweeter <NUM> (<FIG>) is provided instead of speaker array <NUM>, and sound image controller <NUM> is not provided, as in the first exemplary embodiment.

A voice control system <NUM> according to a third exemplary embodiment will be described with reference to <FIG>. The same configurations and functions as those of the first exemplary embodiment and the second exemplary embodiment are designated by the same reference numerals, and the description thereof will be omitted.

Voice control system <NUM> according to the third exemplary embodiment is different from voice control system <NUM> according to the first exemplary embodiment in that it does not have noise reduction controller <NUM> and has seat management unit <NUM>. The low frequency signal of the sound source signal acquired by band controller <NUM> is output to low frequency speaker <NUM> via the D/A converter.

In the first exemplary embodiment, frequency determination unit <NUM> determines the cutoff frequency, based on the content reproduction signal and the noise signal, but in the third exemplary embodiment, a different method is used to determine the cutoff frequency. Frequency determination unit <NUM> stores a cutoff frequency that is determined in advance so as to enable wide band reproduction by complementing each other, based on the reproduction frequency band of speaker array <NUM> and the reproduction frequency band of low frequency speaker <NUM>. For these reproduction frequency bands, it is conceivable to use the nominal specifications of each speaker, or actual measurement values and simulation values in the actual usage environment of the system.

Frequency determination unit <NUM> determines the cutoff frequency by using the cutoff frequency stored in advance. Frequency determination unit <NUM> may use the predetermined cutoff frequency in a fixed manner, or may determine the cutoff frequency according to the characteristics of the content and the settings of the system at the time of content reproduction.

Band controller <NUM> adjusts the sound pressure level of the high frequency signal output from speaker array <NUM> and the sound pressure level of the low frequency signal output from low frequency speaker <NUM>, so that the high frequency range and the low frequency range that user U views can be balanced. The sound pressure level of the low frequency signal and the sound pressure level of the high frequency signal are adjusted according to the seat information such as the bed state, the reclining state, and the like acquired by seat management unit <NUM>, so that it is possible to construct a good sound environment according to the head position of user U in the bed state shown in <FIG> and the head position of user U in the reclining state shown in <FIG>. Low frequency speaker <NUM> may be a speaker having the same configuration and function as control sound speaker <NUM> described in the first exemplary embodiment.

<FIG> and <FIG> show an arrangement example of the microphone and the speaker according to the third exemplary embodiment. In <FIG> and <FIG>, the upper view is a plan view, and the lower view is an elevation view corresponding to the plan view. User U in <FIG> is lying in shell structure <NUM>. Back cushion 90a, seat cushion 90b, and leg cushion 90c are lined up almost flat to be in a bed state. User U in <FIG> is sitting in a chair in shell structure <NUM>. Back cushion 90a, seat cushion 90b, and leg cushion 90c are disposed at different angles to be in a reclining state. User U operates the positions and angles of back cushion 90a, seat cushion 90b, and leg cushion 90c by using the seat operation panel provided on the seat wall, the armrest, and the like, so that the seat state such as the bed state of <FIG>, the reclining state of <FIG>, and the intermediate state thereof can be changed.

In the example shown in <FIG>, low frequency speaker <NUM> is disposed near the head of user U on shell structure <NUM>. In the example shown in <FIG>, low frequency speaker <NUM> is not disposed near the head of user U. On the other hand, speaker array <NUM> is disposed near the head of user U on shell structure <NUM>. As described above, the sound image of the voice signal output from speaker array <NUM> is localized in the vicinity of the head of user U, by the wave field synthesis process by sound image controller <NUM>. Therefore, even if the output of each speaker of speaker array <NUM> is small, it is possible to provide user U with a sufficiently audible volume. Further, since speaker array <NUM> can reduce the sound output in locations other than the location where the sound image is localized by the wave field synthesis process, the risk of sound leakage to the outside of shell structure <NUM> can be reduced. 52a, 52b, 52c, 52d, and 52e in <FIG> show the arrangement of individual speakers located inside speaker array <NUM>. Five speakers 52a to 52e are shown for convenience, but the number of speakers may be other than <NUM>. Speakers 52a to 52e are disposed vertically with respect to the floor surface of shell structure <NUM>. Such an arrangement has an effect of facilitating the wave field synthesis of the voice signal output from each speaker configuring speaker array <NUM> such that the sound emitted by speaker array <NUM> has a directivity so as to be prevented from leaking to the outside of the shell beyond the edge of shell structure <NUM>.

Although the longitudinal direction of speaker array <NUM> is disposed in the vertical direction, the longitudinal direction does not necessarily need to be exactly aligned vertically. For example, the longitudinal direction of speaker array <NUM> may be deviated from the vertical direction and slanted, or when the direction of the edge of shell structure <NUM> is, for example, the horizontal direction or the vertical direction, speaker array <NUM> may be disposed such that the longitudinal direction of speaker array <NUM> is perpendicular to the edge direction of shell structure <NUM>. Further, the intervals between the individual speakers of speaker array <NUM> may be irregular or uniform. When the surface of shell structure <NUM> is a curved structure, the speakers may be disposed side by side along the surface of the curved structure such that the distance between the individual speakers is substantially uniform.

In shell structure <NUM>, content voice detection microphone <NUM> may be provided above the head of user U or the like to detect the content voice leaking to the outside of the shell, and the sound pressure level of the voice output from speaker array <NUM> and low frequency speaker <NUM> may be adjusted such that the voice is equal to or less than the threshold value.

As described above, voice control system <NUM> according to the third exemplary embodiment has the same effect as that of the first exemplary embodiment except for the noise reduction effect even when the noise reduction process is not executed. That is, while preventing sound leakage, it is possible to complement the sounds in different frequency bands with each other by low frequency speaker <NUM> and speaker array <NUM>, and it becomes possible to reproduce the sound of content in a wide band near the head of user U. User U can view the content without using headphones or earphones.

Claim 1:
A voice control device (<NUM>) that controls output of voice signals from a plurality of speakers (<NUM>, <NUM>) including a first speaker (<NUM>) and a second speaker (<NUM>) suitable for outputting higher sound than the first speaker (<NUM>) a predetermined space, comprises:
a sound source signal input unit configured to receive a sound source signal of a content from a sound source;
a sound collection signal input unit (<NUM>) configured to receive a sound collection signal which is collected in the predetermined space and includes a content reproduction signal which is a voice signal of the content output from at least one of the plurality of speakers (<NUM>, <NUM>);
a frequency determination unit (<NUM>) configured to determine a cutoff frequency, based on the content reproduction signal and a noise signal;
a band controller (<NUM>) configured to acquire a high frequency signal in a frequency band equal to or higher than the cutoff frequency and a low frequency signal in a frequency band equal to or lower than the cutoff frequency, from the sound source signal; and
a voice output unit configured to output the low frequency signal to the first speaker (<NUM>), and to output the high frequency signal to the second speaker (<NUM>),
characterized in that
the frequency determination unit (<NUM>) is configured to determine the cutoff frequency based on a frequency or a frequency band in which a sound pressure level of the content reproduction signal is equal to or higher than a sound pressure level of the noise signal.