Toward Advance Open Air PA Systems to Convey Disaster Information Timely and Properly

SUZUKI, YôitiResearch Institute of Electrical Communication & Graduate School of Information Sciences, Tohoku University

Tohoku University is located in Sendai

Sendai is the capital of Miyagi Prefecture & center of Tohoku District of Japan

ca. 1M habitants Epicenter

Nicknamed as a city of green woods

It is located 200 km direct west of the epicenter of the earthquake on 11 March, 2011

Extremely high tidal waves attacked coastal wood (Sendai Plain 仙台平野)

3

March 11, 15:56

（共同通信）http://www.boston.com/bigpicture/2011/03/massive_earthquake_hits_japan.html

The “Disaster public-address radio network”

Most of the rural areas in Japan is covered by out-door public address system This system is calledThis system is called the “disaster public-address (PA) radio network”

Problems revealed by the Tohoku Earthquake

On March 11, 2011Only around half of the citizens got the alarm of extremely high tidal wave by this public PA system

Problems:Tower destructionTower destructionElectric power downLow intelligibilityLow intelligibility

This is what we want to solve!

Low speech intelligibility problem

Long path echo &sound mixture problem

From plural towers, sounds with large delay times of a few to even 10 seconds are mixed to arrive at a listener

It is, therefore, important to describe the detracting characteristics of the long-path echoes on speech intelligibility

This often makes the speech sound hard to understand

This problem, however, has not examined almost at all

reflection

Direct soundreflection

reflection

Long-path echoes make the intelligibility extremely low!

Measurement at Higasi-Matsushima City onNov. 11, 2011

Objective: Measurement of the long-distance acoustic transfer functions with various soundsScheme: As one of Urgent Projects 2011 by RIEC Director’s leadership

Locations of 3 stations measured

Station 41

Station 40

Station 59

Scenes of the measurement on 2 Nov. 2011

deAn example of the impulse responses

Impulse responses corresponding to the ３stations are heavily mixed

0 0.5 1.0 1.5 2.5 3.52.0 3.0 4.0time (s)

Rela

tive

am

plitud

Speech signals convolved with a measured impulse response

A measured impulse response (IR)

Phrase 1Dry source signalSignal convolved with the IRg

Phrase ２Dry source signalSignal convolved with the IR

WordsDry source signalSignal convolved with the IR

A new project for optimal system design

Our efforts 2011 revealed that appropriate design methods of the PA system is highly required

We have got a grant from Ministry of Internal Aff i d C i ti (MIC)

!! !!

Enough intelligible anywhere!!Area A

Area B

Affairs and Communications (MIC)

R&D to improve speech intelligibility

GIS based impulse response estimationsEvaluation of long-path echoes on speech intelligibilityDirectivity control by phased array technologyNetwork based system characteristic control etcNetwork based system characteristic control etc…

・Directivity control for loudspeaker array

High-gainLow-gain

Loudspeaker array

Digital signal proc.

Measurement at Higashi Matsushima on 28-30 May, 2012

ObjectivesMeasurement of PA system directivitiesMeasurement of intelligibility with long-path echoes

約500m東松島　肘曲

P5

約200m

P1(1m)

P2P3

P4

P6

P7

P8

P9

P10

Scenes of intelligibility measurement

Speech intelligibillities weremeasured for speech signalsfrom one and three system(s)

Hearing test of one PA system Hearing test when 3 PA systems mix

Measurement was also held at Arahama (荒浜), a flooded area in Sendai (31 May & 1 Jun 2012

16

Sendai Station

Katahira Campus

Amamiya CampusSeiryo Campus

Sendai City Tagajô City

Kawauchi CampusAobayama Campus

Geographical Survey InstituteNatori City

Total flooded area: 561km2

Measurement in Arahama, Sendai

Transfer functions and directivities were measured sea-coast area of Sendai

仙台荒浜荒浜小学校

P1(1m)

P2P8

P9

仙台荒浜荒浜分団車庫

約200m

約200m

約500m

約500m

P1(1m)

P2

P3

P4

P5

P6

P7 P10

P2 P3 P4

P6

P7

P8

P9

P10

Scenes of measurement in Arahama

Transfer functions and basic characteristics fordirectivity control wereexamined

Our goal for the immediate future

We ara examining estimation & evaluation method of open-air PA system performances

Service area design method of the PA system

!! !!

Enough intelligible anywhere!!Area A

Area B

Optimum design method of the service areas

Colleagues & Acknowledgement

Team membersSaito F, Cui ZL, Sakamoto S (Tohoku University)Iwaya Y (Tohoku Gakuin Univerisity)Morimoto M, Sato H (Kobe University)Usagawa T Chisaki Y (Kumamoto University)Usagawa T, Chisaki Y (Kumamoto University)Takashima H, Aoki M (Nittobo Acoustic Engineering) Sato H (AIST)

A part of this study is supported by:FY2011 RIEC Urgent Cooperative Research ProgramFY2011-12 Grant by Ministry of Internal Affairs and Communications