Patent Publication Number: US-8121298-B2

Title: Hearing aid

Description:
This application is a Rule 1.53(b) Continuation of International Application No. PCT/JP2011/000799 with the International Filing Date of Feb. 14, 2011. 
    
    
     TECHNICAL FIELD 
     The present invention relates to controlling a notification sound in hearing aids mounted on the left and right ears. 
     BACKGROUND ART 
     With a conventional hearing aid, a notification sound is issued to the user in various situations, such as when there is a change in the mode suited to the environment in which the hearing aid is used (hereinafter referred to as program), or when there is a decrease in the remaining battery charge. 
     Many different kinds of information are thus conveyed to the user, and different sounds are generated so that the user can tell them apart. As an example, there is a known technique in which greater variety in the notification sound is afforded by changing the time intervals at which the notification sounds are issued, the number of times they are issued, and so forth. 
     CITATION LIST 
     Patent Literature 
     
         
         Japanese Laid-Open Patent Application 2009-253343 
       
    
     SUMMARY 
     However, with a conventional hearing aid in which the user distinguishes among notification sounds by means of how many times they are issued, although there is no problem when the hearing aid is worn on only one ear, if it is worn on both ears there may be a difference in the distance from the operating unit between the left and right hearing aids, for example, and this may cause a discrepancy timing at which the notification sounds are generated from the left and right hearing aids. In this case, the user ends up hearing the notification sound more times than it was intended to be issued, making it difficult to ascertain the type of notification sound. 
     In view of this, it is an object of the present invention to provide a binaural hearing aid with which it is easy to catch notification sounds, which is accomplished by controlling the timing at which the notification sounds are generated by the two hearing aids. 
     The hearing aid pertaining to the present invention is mounted on the left and right ears, respectively, and generates a notification sound that notifies the user of a state change, said hearing aid comprising a first hearing aid and a second hearing aid mounted on the left and right ears, respectively. The first and second hearing aids each have a communication unit, an operating unit, a notification sound generator, and a notification sound generation delay unit. The communication unit performs communication between the first and second hearing aids. The operating unit changes the operating state of the first and second hearing aids. The notification sound generator generates a notification sound when the operating state of the first and second hearing aids is changed due to operating of the operating unit. The notification sound generation delay unit controls the notification sound generator of the second hearing aid or the first hearing aid so as to delay by a specific amount the timing at which a notification sound is generated by the notification sound generator in the first hearing aid or the second hearing aid, on the basis of delay time information received through the communication unit. 
     The above-mentioned state change of the hearing aid includes a case in which the sound volume of the left and right hearing aids is changed, a case in which the speech processing program for optimally performing hearing aid processing in the left and right hearing aids is switched, and so forth. The above-mentioned notification sound includes beeping sounds (electronic sounds) such as “beep,” “beep-beep,” and “beep-beep-beep,” as well as melodies, human speech, and so forth. 
     With the binaural hearing aid of the present invention, the timing at which the notification sounds are generated by the hearing aids mounted on both ears is controlled so that, for example, the timing at which the notification sounds generated by the left and right hearing aids will be clearly shifted so as not to overlap, or the timing at which the notification sounds generated by the left and right hearing aids is synchronized rather than being shifted, which makes it easier for the user to catch the notification sounds. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a concept diagram of the configuration of the hearing aid pertaining to an embodiment of the present invention; 
         FIG. 2  is a block diagram of the configuration of the hearing aid in  FIG. 1 ; 
         FIG. 3  is a block diagram of a notification sound output controller included in the hearing aid in  FIG. 2 ; 
         FIG. 4  is a diagram of the configuration of a packet sent to and from the hearing aid in  FIG. 1 ; 
         FIG. 5  is a diagram illustrating when a notification sound is incorrectly recognized; 
         FIGS. 6   a  to  6   e  are diagrams illustrating details of how the notification sound generation timing is synchronized by the hearing aid in  FIG. 1 ; 
         FIG. 7  is a diagram illustrating the notification sound generation timing with a hearing aid pertaining to another embodiment of the present invention; 
         FIGS. 8   a  to  8   d  are diagrams illustrating details of how notification sounds are generated asynchronously with another embodiment of the present invention; and 
         FIGS. 9   a  to  9   c  are diagrams illustrating the state when the program is switched with a hearing aid in another embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The hearing aid pertaining to an embodiment of the present invention will now be described in detail through reference to the drawings. 
     Embodiment 1 
       FIG. 1  shows the configuration of the hearing aid in this embodiment, and is a concept diagram of a pair of left and right hearing aids is used for binaural application, and shows the state when a right-ear hearing aid  10 R (a first hearing aid) and a left-ear hearing aid  10 L (a second hearing aid) are each put on. 
     The hearing aids  10 L and  10 R are connected to each other via wireless communication  30 , which allows the hearing aids  10 L and  10 R to exchange information about programs, volume changes, and so forth. A remote control  20  sends the two hearing aids information about programs, volume changes, and so forth. 
       FIG. 2  is a block diagram that applies to both of the hearing aids  10 L and  10 R. 
     Ambient sound inputted from a microphone  101  is outputted as an analog speech signal  120 . This signal is converted into a digital speech signal by an A/D converter  102 , after which it is outputted as a digital speech signal  121 . This signal is then subjected to various kinds of signal processing, including hearing aid processing, by a hearing aid processor  105 , and then outputted as a speech signal  122  to a mixer  109 . 
     A notification sound generator  108  generates a notification sound that notifies the wearer of battery failure, a program switch, etc., and outputs a notification sound signal  130  to the mixer  109 . 
     The mixer  109  mixes the speech signal  122  that has undergone hearing aid processing and been outputted from the hearing aid processor  105 , with the notification sound signal  130  outputted from the notification sound generator  108 , and outputs the result as a digital speech signal  123  to a D/A converter  110 . 
     The D/A converter  110  converts the digital speech signal  123  outputted from the mixer  109  into analog speech data, and outputs this as an analog speech signal  124 . 
     A receiver  111  converts the analog speech signal  124  into air vibrations, which are outputted as sound information that can be heard by the wearer. 
     We will divide up the description here into a case in which the wearer manipulates either the hearing aid  10 L or  10 R to directly switch the operation of that hearing aid  10 L or  10 R, and a case in which the operation of one of the hearing aids  10 L and  10 R is switched according to a command received by the other hearing aid. 
     First, we will describe a case in which the wearer directly manipulates the hearing aid  10 L or  10 R for which the state is to be changed, and thereby switches the operation of that hearing aid. 
     The hearing aid processor  105  is connected to a volume adjuster  106  (operating unit) and a program selector  107  (operating unit) that are in the form of switches. Consequently, the wearer himself can adjust the volume with the volume adjuster  106 , and can switch the program of the hearing aids  10 L and  10 R by manipulating the program selector  107 . 
     A speech adjustment control signal  125  produced when the volume adjuster  106  is manipulated and a program change control signal  126  produced by the program selector  107  are inputted to the hearing aid processor  105 . After the volume has been set or the program switched, that signal is outputted to a notification sound output controller  104 . 
     The above-mentioned programs are speech processing programs for performing optimal hearing aid processing as dictated by the situation, such as whether the surroundings are noisy or quiet. In this embodiment, for example, the programs are divided into four types, from program A to program D, which are switched by user operating. 
     The volume adjuster  106  comprises up and down button. Pressing the up button increases the volume, and pressing the down button reduces the volume. More specifically, the volume is set from −32 dB to 0 dB, and each time the button is pressed it results in a change of 2 dB in the volume. 
     The notification sound output controller  104  determines whether or not a notification sound is necessary on the basis of data inputted as a control signal  127  or a control signal  128 . If a notification sound is necessary, the notification sound output controller  104  outputs the type of notification sound as notification sound information  129  after a specific length of time has elapsed. 
     The notification sound output controller  104  also outputs the inputted control signal  127  directly to a communication unit  103  as the control signal  128 . The communication unit  103  then sends the received control signal  128  as a wireless control signal  131  to the other of the hearing aids  10 L and  10 R, the one that was not directly manipulated by the wearer. 
     After receiving the notification sound information  129 , the notification sound generator  108  outputs a notification sound corresponding to the type of notification sound. 
     As to whether or not a notification sound needs to be generated when a change in the state of the hearing aids  10 L and  10 R has been detected, this may be determined in accordance with the manufacturing and design intentions, such as when a notification sound is generated in the event of a program switch, for example, but there is no need to generate a notification sound in the event of a volume change. 
     Next, we will describe a case in which one hearing aid  10 L receives the wireless control signal  131  from the other hearing aid  10 R. Here, we will describe an example in which the hearing aid  10 L receives the wireless control signal  131  from the hearing aid  10 R, but the hearing aids  10 L and  10 R may be in the opposite relation. 
     The communication unit  103  outputs the wireless control signal  131  received from the hearing aid  10 L to the notification sound output controller  104  as the control signal  128 . 
     The notification sound output controller  104  determines whether or not a notification sound is necessary, and if it is necessary, the notification sound information  129  required to generate the notification sound is outputted to the notification sound generator  108 . Upon receiving the notification sound information  129 , the notification sound generator  108  outputs the notification sound signal  130  to the mixer  109 . 
     Next, the notification sound output controller  104  will be described in detail through reference to  FIG. 3 . 
     The notification sound output controller  104  is constituted so as to include a notification sound generation decider  200  and a notification sound generation delay unit  201 . 
     The notification sound generation decider  200  confirms the type of notification sound and the notification sound generation timing on the basis of the inputted control signal  128  or control signal  127 . 
     The notification sound generation delay unit  201  delays the output of the notification sound information  129  until a specific amount of time has elapsed, on the basis of delay time information included in the control signal  128  or the control signal  127 . In this embodiment, controlling this notification sound generation timing allows the output of the notification sounds produced by the left and right hearing aids  10 L and  10 R to be shifted (asynchronously) so that they are not outputted at the same time. This delayed output of the notification sound will be discussed in detail below. 
     Next, the timing of the notification sounds outputted from the left and right hearing aids  10 L and  10 R will be described. 
     Here, as an example of a notification sounds that are outputted, we will assume that the above-mentioned programs A to D are switched so that the outputted notification sound (beeping sound) is a “beep” (one time) in program A, a “beep, beep” (two times) in program B, a “beep, beep, beep” (three times) in program C, and a “beep, beep, beep, beep” (four times) in program D. 
     For example, if the selected program is switched to program B so that a notification sound is generated two times by each of the left and right hearing aids  10 L and  10 R, as shown in  FIG. 5 , the timing at which the notification sounds are generated at the hearing aids  10 L and  10 R may end up deviating. If the notification sounds are outputted alternately at the left and right hearing aids  10 L and  10 R at this point, the wearer will hear a mixture of four notification sounds from the left and right ears, so there is the risk that the wearer will accidentally think the program has been switched to D, in which a notification sound is emitted four times. 
     One possible cause of such deviation in the timing at which the notification sounds are generated from the left and right hearing aids  10 L and  10 R is a case in which a command is sent from the remote control  20  to the hearing aids  10 L and  10 R, but because the left and right sides are linked, the transmitting hearing aid does not receive the command sent from the remote control. At this point, the hearing aid that has received the command resends the command to the other hearing aid, and timing deviation can occur in this process. Also, when just one hearing aid is manipulated, the command may not be received just as with remote control operation, or there may be timing deviation between the hearing aids  10 L and  10 R due to the transmission time required to send a command from one to the other, or timing deviation may occur when there is a different in the processing speed inherent to each hearing aid from the time a command is received until a notification sound is generated. Thus, it takes time to communicate a notification sound generation from one of the hearing aids  10 L and  10 R to the other, until the notification sound is generated on the side of the hearing aid that has received this communication, so there is a delay in the generation of the notification sounds between the left and right hearing aids  10 L and  10 R. 
     With the hearing aids  10 L and  10 R in this embodiment, this problem is solved by controlling the timing at which notification sounds are generated so that the notification sounds emitted from the hearing aids  10 L and  10 R are completely synchronized, as shown in  FIGS. 6   a  to  6   e , which is done to make it easier for the wearer of the hearing aids  10 L and  10 R worn on the left and right ears to hear the notification sounds. Consequently, the generation of notification sounds between the left and right hearing aids  10 L and  10 R can be completely synchronized, so the wearer can clearly identify the type of notification sound emitted. 
     The synchronization control of the notification sound generation timing will now be described in detail through reference to  FIGS. 6   a  to  6   e.    
       FIG. 6   a  illustrates the basic operation of the hearing aids  10 L and  10 R, which perform wireless communication. 
     The hearing aid  10 R and the hearing aid  10 L periodically communicate with each other at intervals of 40 ms. This periodic communication between the hearing aids  10 L and  10 R has two purposes: one is to confirm that the other hearing aid is within the range of communication, and the other is to send control signals, various parameters, and so forth to the other hearing aid. 
       FIGS. 6   b ,  6   c , and  6   d  show an example of control for synchronizing the timing in the generation of notification sounds produced when a program is switched. 
     First, as shown in  FIG. 6   b , the hearing aid  10 R, which has undergone a program switch via the program selector  107  by the wearer, is in a state in which a notification sound can be generated right away, but notification sound generation is not carried out immediately after this, and a notification sound is instead generated at the timing of the next periodic communication. 
     Here, periodic communication must be carried out at 40 ms intervals in order for the hearing aid  10 R to tell the hearing aid  10 L to make a notification sound. Therefore, if a notification sound is made at the same time that a program is switched on the hearing aid  10 R side, the timing at which the notification sound is made will deviate by a maximum of 40 ms from that of the hearing aid  10 L. Thus, in this embodiment, in order to prevent this deviation in the timing at which the notification sound is generated, control is performed so as to delay the generation of the notification sound on the hearing aid  10 R side, where it is possible that a notification sound will be generated first. 
     More specifically, the notification sound generation delay unit  201  retards the generation of the notification sound by notifying the notification sound generator  108  later by the amount of time remaining from when the program is switched with the program selector  107  until the next transmission timing. 
     Consequently, the timing for generating the notification sound can be matched to the other hearing aid  10 L. 
     With a hearing aid in which periodic communication is not performed between the hearing aids  10 L and  10 R, the time until the next transmission timing is not taken into account, and the other hearing aid  10 L can be notified at the same time the program is switched, but as will be discussed below, the notification sound generation timing may be controlled by taking into account the processing time of the digital signal processor (DSP) and the time it takes for communication. 
     Next, we will describe an example in which the time communication actually takes, that is, the communication speed, is a factor that causes deviation in the notification sound generation timing between the hearing aids  10 L and  10 R. 
     As to communication speed, what speed of communication to employ, such as high-speed communication or low-speed communication, is a design matter, but low-speed communication is often used because of its lower cost and power consumption. When low-speed communication is used, there is the risk that the communication time may adversely affect the synchronization of notification sound generation. The term “communication speed” refers to how much data can be transferred in one second. The better is this ability, the higher is the communication speed, and the worse is this ability, the lower is the communication speed. Also, at a given communication speed, more communication data, that is, a larger packet size, is included in the idea of slower communication because it takes longer for the communication of one packet. 
     Here, if we let Δtr be the time from the start of communication of the one hearing aid  10 R until the completed receipt by the other hearing aid  10 L, as shown in  FIG. 6   c , the hearing aid  10 R generates a notification sound after the elapse of the time Δtr after the hearing aid  10 L has been notified of switched program information. Meanwhile, the hearing aid  10 L generates a notification sound simultaneously with the hearing aid  10 R at the point of receiving this notification. 
     That is, with the notification sound generation delay unit  201  on the hearing aid  10 R side, the time obtained by adding Δtr to the remaining time from when the program was switched via the program selector  107  until the timing of the next transmission is set as the delay time, and this is sent to the notification sound generator  108  so that the notification sound will be delayed more than usual. Consequently, the timing at which the notification sounds are generated by the hearing aids  10 L and  10 R can be synchronized. 
     Next, we will describe an example in which the operation speed of DSP computation processing or the like is a second factor that causes deviation in the notification sound generation timing between the hearing aids  10 L and  10 R. 
     Just as with the communication speed discussed above, when lower cost and power consumption are taken into account, a DSP with lower processing speed is usually used for the hearing aids  10 L and  10 R. Accordingly, the processing speed of this DSP must be taken into account in the synchronization of the notification sound generation timing. 
     As shown in  FIG. 6   d , if we let Δsr be the DSP processing speed (processing time), the notification sound output controller  104  of the hearing aid  10 R on the transmission side generates a notification sound after the elapse of a time obtained by adding the sum of Δtr+Δsr to the remaining time from when the program was switched via the program selector  107  until the next transmission timing. After receiving a notification sound generation notification, the hearing aid  10 L necessarily generates a notification sound after the elapse of the time Δsr. As a result, the timing at which the notification sounds are generated by the hearing aids  10 L and  10 R can be synchronized. 
       FIG. 6   e  is an example of when a notification sound is issued after checking that the hearing aid  10 L has indeed received the information sent by the hearing aid  10 R. 
     The hearing aid  10 R sends the hearing aid  10 L switched program information and delay time information (the time Δtr) as soon as a program is switched by the wearer via the program selector  107 . 
     Upon receiving this notification, the hearing aid  10 L generates a notification sound after the elapse of the time Δtr, simultaneously with the return of an acknowledge signal to the hearing aid  10 R, at the next transmission timing. The hearing aid  10 R generates a notification sound at the point when the acknowledge signal is received. 
     Although not shown in  FIG. 6   e , depending on the DSP processing capability of the hearing aids  10 L and  10 R, it may be preferable for the delay time to take Δsr into account as shown in  FIG. 6   d.    
     Consequently, it can be confirmed that the hearing aid  10 L (on the receiving side) has definitely received the information sent from the hearing aid  10 R, and notification sounds can be generated simultaneously from the hearing aids  10 L and  10 R. 
     The delay time Δsr is set at the design stage in the case of a model in which the hearing aids  10 L and  10 R mounted on both ears both have the same function, so this delay time can be stored in the main bodies of the hearing aids  10 L and  10 R ahead of time. On the other hand, when using a model in which the functions are different for the left and right ears, such as when a hearing aid for a patient with severe hearing impairment is used on one ear and a hearing aid for a patient with mild hearing impairment is used on the other ear, a different DSP may be installed in each of the hearing aids, or there may be a difference in the delay time Δsr between the hearing aids  10 L and  10 R. In such a case, delay time information may be shared between the left and right hearing aids by conveying information related to the delay time Δsr via the communication unit  103  and through a communication packet. 
     The communication packed sent and received by the hearing aids  10 L and  10 R in this embodiment will now be described through reference to  FIG. 4 . 
     A packet is mainly divided into a command region that identifies the type of command, a parameter region containing parameters, and a delay time region that specifies the notification sound generation timing. 
     Program changes, changes to the volume of the output sound, remaining battery charge warnings, and other such types of commands are stored as numerical values in the command region. Also, parameters for those commands, such as one of programs A to D in the case of a program change, are stored in the command region, and in the case of a volume change, a numerical value from −32 dB to 0 dB is stored. The delay time information discussed above is stored in the delay time region. 
     If no periodic communication is performed between the left and right hearing aids  10 L and  10 R, the time until the above-mentioned next transmission timing is not taken into account, and a notification may be sent to the hearing aid on the other side simultaneously with a program switch. 
     Consequently, the one hearing aid  10 R can ascertain the processing capability of the other hearing aid  10 L, so the proper delay time can be set to allow notification sounds to be generated at the same time. 
     Next, we will describe a case in which the hearing aids  10 L and  10 R are operated remotely with the remote control  20  (see  FIG. 2 ). 
     Usually, the operation of both the hearing aids  10 L and  10 R is switched by operation of the remote control  20 , but in rare situations a wireless control signal  305  may reach only one of the hearing aids due to the reception state of the hearing aids  10 L and  10 R. In a case such as this, a problem is that the operation is switched at only one of the hearing aids. 
     In this embodiment, to solve this problem, the hearing aids  10 L and  10 R notify each other of notification sound generation as shown in  FIG. 6   e  when the wireless control signal  305  is received from the remote control  20 , and control is performed so that notification sounds are generated after the hearing aids  10 L and  10 R have exchanged information (acknowledge signals) to the effect that the wireless control signal  305  has been received. 
     As discussed above, with the hearing aids  10 L and  10 R of this embodiment, even when they are worn on both ears, the timing at which notification sounds are generated at the hearing aids  10 L and  10 R is controlled so that the notification sounds can be generated at the same time from the hearing aids  10 L and  10 R. As a result, the wearer can clearly distinguish between types of notification sounds, and an accurately hear them without any recognition error. 
     Embodiment 2 
     The hearing aid pertaining to another embodiment of the present invention will now be described through reference to  FIGS. 7 to 9   c.    
     With this embodiment, the control differs from that in Embodiment 1 above in that asynchronous control is performed in which the separate notification sounds emitted from the hearing aids  10 L and  10 R are completely offset so that they can be distinguished apart, and this is done as control for making it easier for the wearer of the hearing aids  10 L and  10 R mounted on the left and right ears to hear the notification sounds. 
     In this embodiment, those units that have the same function as in Embodiment 1 above will be numbered the same, and will not be described again. 
     With the hearing aids  10 L and  10 R in this embodiment, to solve this problem, as shown in  FIG. 7 , the notification sound generation timing is controlled so that upon completion of the generation of the notification sound outputted first from among the hearing aids  10 L and  10 R, the notification sound on the side generated later is generated after the elapse of a specific length of time. Consequently, the generation of notification sounds can be completed separated temporally between the left and right hearing aids  10 L and  10 R, so the wearer can clearly recognize the type of notification sound. 
     Next, the asynchronous method for notification sound generation timing will be described through reference to  FIGS. 8   a  to  8   d.    
     First, the basic operation in a case in which wireless communication is performed between the left and right hearing aids  10 L and  10 R will be described through reference to  FIG. 8   a.    
     In this embodiment, the hearing aid  10 R and the hearing aid  10 L periodically sent information to each other at intervals of 40 ms. The periodic communication between the hearing aids  10 L and  10 R serves two purposes: confirming whether or not the other hearing aid is within communication range, and sending various parameters, control signals, and so forth to the other hearing aid. 
       FIGS. 8   b  and  8   c  show an example of control for generating notification sounds that are asynchronously offset from one another when the program has been switched. 
     First, as shown in  FIG. 8   b , the hearing aid  10 R, for which the program has been switched by the wearer, generates a notification sound immediately after this switch. The hearing aid  10 R sends the hearing aid  10 L delay time information and switched program information as a notification sound generation notification. We will assume that this notification sound generation notification includes program information for a setting change performed by the hearing aid  10 L, and delay time information specifying the notification sound generation timing, within a communication packet (discussed below). 
     Again in this embodiment, just as in Embodiment 1 above, the communication packet shown in  FIG. 4  is used as the communication packet sent to and received by the hearing aids  10 L and  10 R. 
     The delay time stored in this communication packet is the timing for generating a notification sound at the hearing aid  10 L, and is the length of time until the end of notification sound generation at the hearing aid  10 R. As to the notification sound generation duration, a single notification sound generation time is 160 ms, followed by a non-generation time of 160 ms to make up a set, and this set of 320 ms is termed the notification sound generation duration. For example, with a notification sound indicating a switch to program B, since a two-time notification sound is generated with program B, a time of 640 ms (two sets) is necessary. This delay time is conveyed to the hearing aid  10 L, whereupon notification sound generation at the hearing aid  10 L is started after the end of notification sound generation at the hearing aid  10 R. As a result, notification sounds can be generated from the left and right hearing aids  10 L and  10 R in a state of complete separation, without any overlap between the two. 
       FIG. 8   c  is an example of processing for confirming that the notification sound generation notification sent by the hearing aid  10 R has indeed been received by the hearing aid  10 L. It is conceivable that the notification sound generation notification will not arrive, and this is a contingency for such a case, in which the notification sound generation notification is retried a number of times. 
     When the wearer has switched the program for the hearing aid  10 R, that hearing aid notifies the hearing aid  10 L of switched program information and delay time information. The hearing aid  10 L returns an acknowledge signal at the next transmission timing, and generates a notification sound after the elapse of a delay time based on the received delay time information. 
     If the communication state between the left and right hearing aids  10 L and  10 R is so poor that the hearing aid  10 L does not receive the notification sound generation notification, the hearing aid  10 L cannot return an acknowledge signal. If no acknowledge signal comes back, a notification sound generation notification is sent again to the hearing aid  10 L. 
     At this point, the delay time set by the hearing aid  10 R must be adjusted for the delay in notification since the notification sound generation notification was resent. In this case, communication fails with the first notification sound generation notification, but succeeds with the second notification sound generation notification, so the delay is only 80 ms from the first notification until the second notification. Thus, the delay time conveyed to the hearing aid  10 L is reset to 560 ms, which is obtained by subtracting this time of 80 ms. 
     Consequently, after confirming that the other hearing aid  10 L has indeed received the notification, the timing at which the notification sounds are outputted from the hearing aids  10 L and  10 R can be clearly offset so that there is no overlap. 
     In this embodiment, the hearing aid  10 R generates a notification sound as soon as the program is switched by the wearer, but the control may be such that a notification sound is generated at the point when an acknowledge signal is received from the hearing aid  10 L. 
     Next, a case in which the hearing aids  10 L and  10 R are remotely operated with the remote control  20  will be described. 
     As shown in  FIG. 2 , the remote control  20  comprises a communication unit  301  that communicates with the hearing aids  10 L and  10 R, a controller  302  that controls the function of the remote control  20 , a volume adjuster  303  that adjusts the volume of the hearing aids  10 L and  10 R, and a program selector  304  for switching the program. The volume adjuster  303  and the program selector  304  are provided to the remote control  20  as switch-like constituent members. 
     For example, when the remote control  20  is used to change the volume of the hearing aids  10 L and  10 R, the volume adjuster  303  is operated so that a volume adjustment control signal  310  is sent as a wireless control signal  305  through the controller  302  and the communication unit  301  to the hearing aids  10 L and  10 R. Just as when the program is switched, a program change control signal  311  is sent as a wireless control signal  305  from the program selector  304 , through the controller  302  and the communication unit  301 , to the hearing aids  10 L and  10 R. 
     Usually, the operation of both of the hearing aids  10 L and  10 R is switched by operation of the remote control  20 , but when the hearing aids  10 L and  10 R generate notification sounds at the same time, as discussed above, there is the risk that the notification sound generation from the left and right hearing aids  10 L and  10 R will be offset due to factors such as communication errors and processing speed. 
     In this embodiment, this problem is solved by having the hearing aids  10 L and  10 R alternately communicate with each other periodically (every 40 ms). This alternate communication refers to alternately switching the communication direction from the hearing aid  10 R to the hearing aid  10 L, and then from the hearing aid  10 L to the hearing aid  10 R, as discussed above. 
     As shown in  FIG. 8   d , when the hearing aids  10 L and  10 R both receive notification sound generation notifications from the remote control  20 , the side capable of transmission performs notification sound generation notification to the other side. 
     In  FIG. 8   d , after a notification sound generation notification from the remote control  20  is received, communication from the hearing aid  10 R to the hearing aid  10 L is first. Therefore, the hearing aid  10 R starts generating a notification sound at this point, and sends a notification sound generation notification to the hearing aid  10 L. Having received the notification sound generation notification, the hearing aid  10 L generates a notification sound after the designated delay time. Consequently, the timing at which the notification sounds are generated can be clearly shifted between the hearing aids  10 L and  10 R. 
       FIG. 9   a  shows the state when the hearing aid  10 R has been switched to program B. 
     Having had its program switched by the wearer, the hearing aid  10 R generates a notification sound, after which it sends a notification sound generation notification to the hearing aid  10 L at the point of completion of notification sound generation 640 ms later. The hearing aid  10 L generates a notification sound after receiving the notification sound generation notification. 
     With this method, the completion of notification sound generation by the hearing aid  10 R acts as a trigger for performing switch notification to the hearing aid  10 L. Accordingly, there is no need to notify the hearing aid  10 L on the other side of the delay time, and this control can be accomplished more easily. 
       FIGS. 9   b  and  9   c  show the flow in returning an acknowledge signal after receipt of a notification sound generation notification. 
     As shown in  FIG. 9   b , having received the notification sound generation notification, the hearing aid  10 L returns an acknowledge signal at the next communication timing, and notifies the hearing aid  10 R of its safe receipt of the signal. Consequently, the hearing aid  10 R confirms that the notification sound generation notification has been properly transmitted, after which the operation is ended. 
       FIG. 9   c  shows the processing when a notification sound generation notification sent by the hearing aid  10 R did not reach the hearing aid  10 L for one reason or another. 
     In this case, the hearing aid  10 L cannot return an acknowledge signal because no notification sound generation notification was received. In view of this, notification sound generation notification is performed again by the hearing aid  10 R to which no acknowledge signal was returned. This allows a notification sound generation notification to be sent more reliably to the hearing aid  10 L on the other side. 
     As discussed above, with the hearing aids  10 L and  10 R in this embodiment, even when hearing aids are worn on both the left and right ears, the notification sounds can be clearly heard by the wearer because the timing at which the notification sounds are generated from the hearing aids  10 L and  10 R is controlled, and the timing at which the notification sounds are outputted from the hearing aids  10 L and  10 R is clearly shifted. 
     Other Embodiments 
     (A) 
     In Embodiments 1 and 2 above, an example was described in which a beeping sound (electronic sound), such as “beep” or “beep, beep,” was made as the notification sound according to the selected program, but the present invention is not limited to this. For instance, a melody, human speech, and so forth may be used as the notification sound instead of what was discussed above. 
     (B) 
     In the above embodiments, an example was described in which the state change of the hearing aids  10 L and  10 R was a switch of programs or volume via the hearing aids themselves or the remote control  20 , but the present invention is not limited to this. For instance, a switch may be performed automatically according to the surrounding environment, or another state change related to the hearing aids may be detected and the above-mentioned control carried out. 
     Industrial Applicability 
     The hearing aid pertaining to the present invention controls the timing at which notification sounds from two hearing aids are generated, making it easier for the wearer to hear the notification sounds, and therefore is expected to find wide application as a binaural hearing aid. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10 L hearing aid (second hearing aid) 
               10 R hearing aid (first hearing aid) 
               20  remote control 
               30  wireless communication 
               101  microphone 
               102  A/D converter 
               103  communication unit 
               104  notification sound output controller 
               105  hearing aid processor 
               106  volume adjuster (operating unit) 
               107  program selector (operating unit) 
               108  notification sound generator 
               109  mixer 
               110  D/A converter 
               111  receiver 
               120 ,  124  analog speech signal 
               121 ,  122 ,  123  digital speech signal 
               125  speech adjustment control signal 
               126  program change control signal 
               127 ,  128  control signal 
               129  notification sound information 
               130  notification sound signal 
               131  wireless control signal 
               200  notification sound generation decider 
               201  notification sound generation delay unit 
               301  communication unit 
               302  controller 
               303  volume adjuster (operating unit) 
               304  program selector (operating unit) 
               305  wireless control signal 
               310  volume adjustment control signal 
               311  program change control signal