防災・減災情報を効果的に伝送する
メッシュネットワーク型インテリジェント
拡声システムの研究開発
苣木 禎史（熊本大学）
北須賀 輝明，山田 文彦（熊本大学）
坂本 修一（東北大学）	

→Information ﬂow on warning system
multiple paths to deliver disaster messages.
Sensors
Cabinet office( 内閣府 )e.g. Seismometer( 地震計 )Rain guage( 雨量計 )Water level guage( 水位計 )Land observation satellite( 観測衛星 )Survaillance camera( 監視カメラ )Prime Minister’ s official residence( 首相官邸 )Fire and Disaster Management Agency( 総務省消防庁 )Ministry of Land, Infrastructure and Transport and Tourinsm( 国土交通省 )Japan Meteorological Agency( 気象庁 )Prefectural and municipal governments: Local disaster management headquarters( 県市町村自治体災害対策本部 )2	

Topic : Disaster mitigation utilizing public address

In the Great East Japan Earthquake, among residents who could
obtain evacuation announcements in the affected prefectures, 45% ofthem obtained it from outdoor loudspeakers.
However, among those who obtained evacuation announcementsfrom outdoor loudspeakers, only 56% of them answered they could
clearly hear the announcements.
3	Topic : Disaster mitigation utilizing public address

Problems :Residents in a house.
Difﬁculty on hearing in a ﬁeld.

Reasons :Overlapping of sounds from other public address systemor reﬂected sounds by building, mountain, woods, andso on.
4	Topic : Disaster mitigation utilizing public address
What functions are expected?
l Timing controll Sound pressure level controll Directivity control
Sound overlapping
Pattern A: Service area

SNRRain: Service area

Wind / Temperature
WindWind: Service area

Pattern BControl
Pattern C5	

Topic : Disaster mitigation utilizing public addressl Timing control is implemented to improvesignal to interference ration at overlapped area.

6	Emission timing controller	• Emission timing control

7	Emission timing controller	• Emission timing control

8	Processing time
• total delay from input to output

τn = τck+τtkn+τdn+τwn+τcn

Block diagram

9	

Errors on each block
total delay τn=τck+τtkn+τdn+τwn+τcn
τck, τcn : A/D, D/A conversion
τtkn : transmission time
1 frame data(bits) / throughput(bps)depends on network.
e.g. PCM 16 bits, 1 frame = 1024 samples,
LTE 2 Mbps < 10 ms
τdn : sound event detection
e.g. 10 ms(ITU G7.29 AnnexB)τwn : emission timing control
10	Intelligent public address system
The detailed system and its performance is described inEmission timing control method for improving signal to interference
ratio on public address system
Taira Onoguchi, , Dan Murakami, Yoshifumi Chisaki
Applied Acoustics

Volume 98, November 2015, Pages 70–78

11	Demonstration(Residents in Kurokami area, move to higher place in Japanese.)12	Functions to increase reliability	

• Automatic network selector• Nodes and a server automatically change their default gateway toselect the active and widest bandwidth network.
Default(gateway

Default(gatewayNetwork(device(ANetwork(device(ANetwork(device(BNetwork(device(BNodeNodeVPN

VPN

VPN Server

13	

Functions to increase reliability	

• Fail safe structure for network disorder• If all of network devices of a node are down,other nodes determine emission timing without considering thatnode.
Network(device(ANetwork(device(BVPN

Node ATime(outVPN

Send(queryVPN Server

Network(device(ANetwork(device(BNode B

Node B

14	

Functions to increase reliability	

• Monitoring own emission and environmental sound• Monitoring own daily announcements to checkthe status of sound output.

Other nodes
“Pass”*or*“Fail”
Input*signal

Sound*device*check**by*cross7correla:on

Node  Microphone*for*monitoring

15	

Functions to increase reliability	

• Emission sound level enhancement• Status of sound output is shared with other nodes.
• If sound output of the adjacent node is down, the node increases its
emission sound level.
NodeNodeGain&controller

Gain&controller

“Fail”Sound&device&check&&by&cross1correla4on

Adjacent Node Enhancement	16	Conclusions• Intelligent public address system with a network connection isintroduced.
• Since the algorithm is simple, implementation on a single board
computer is easy.
• Estimation of direct and reﬂected sounds is proposed.
Future works:• Experiments in a ﬁeld.
• Mapping system will be developed.

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