Looping the London Tube

for: 2nd International Hearing Loop Conference by:

Edworthy Audio Engineering Consultants Tel: +44(0)1435 830195 E-mail: [email protected]

Web: www.edworthyaudio.com

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The 21 st Century London Underground (The Tube) What Transport for London (TfL) wanted What we found in our survey of stations The ‘Reality Check’ The solutions (c) Edworthy Audio Engineering Consultants DGEA QT035_01 2

The 21 st Century Tube DGEA QT035_01 (c) Edworthy Audio Engineering Consultants 3

The 21 st Century Tube DGEA QT035_01    Serves 270 stations and has 250 miles of track  2 nd longest metro system in the world after Shanghai Metro In 2007, more than one billion passenger journeys  3 rd busiest metro system in Europe after Moscow and Paris Run by Transport for London (TfL) (c) Edworthy Audio Engineering Consultants 4

DGEA QT035_01 UK Disability Discrimination Act (DDA) 1995 and 2005    Requires those supplying services to not discriminate against those with disabilities Must provide additional facilities unless it is unreasonable to do so Replaced in 2010 by ‘Disability and the Equality Act’  Similar requirements (c) Edworthy Audio Engineering Consultants 5

What Transport for London wanted DGEA QT035_01 (c) Edworthy Audio Engineering Consultants 6

What Transport for London wanted DGEA QT035_01    TfL needed to minimise the risk of litigation under the DDA Underground stations are acoustically very noisy and reverberant  Makes very bad conditions for using hearing aid microphone So, there was a requirement for loops in all public parts of The Tube (c) Edworthy Audio Engineering Consultants 7

The London Underground Loop Survey Project DGEA QT035_01 (c) Edworthy Audio Engineering Consultants 8

The London Underground Loop Survey Project DGEA QT035_01     Loops in all public parts of The Tube?!

Electric traction power supplies are high current = high magnetic field Concern that environmental magnetic noise would make loops impractical in many places In 2002 asked Edworthy Audio Engineering Consultants to discover true situation (c) Edworthy Audio Engineering Consultants 9

Two questions the survey was designed to answer DGEA QT035_01    Is background magnetic noise going to be a problem to hearing-aids users?

 If so, is this general or restricted to certain areas? Do the metals used in station construction have an effect on the performance of loop systems?

 If so, does this make loop systems impractical?

Would it be unreasonable to expect loops ?

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How we decided to find out DGEA QT035_01    Survey of seven representative stations   Deep tunnel, partially covered, and surface station Ticket halls, routeways, platforms Magnetic noise survey Temporary loop installations and measurement of the loop field to assess effects of structural metal (c) Edworthy Audio Engineering Consultants 11

DGEA QT035_01 How we conducted the noise survey    Calibrated hand-held loop field-strength meters Measured during normal working hours  All electrical equipment assumed ON Measured the vertical field at heights expected for hearing aids (c) Edworthy Audio Engineering Consultants 12

DGEA QT035_01 What noise limits did we set?

 Project was before the revised international standard (IEC 60118-4:2006), so we set our own signal-to-noise criteria    >42dB = user is unlikely to notice interference 42dB to 27dB = user is likely to notice and find it mildly to significantly disturbing <27dB = user may find the interference very disturbing and the loop unusable (c) Edworthy Audio Engineering Consultants 13

DGEA QT035_01 Where did we check for noise?

     Ticket halls   General area Ticket windows Walkways Escalators Platforms Passenger Help Points everywhere (c) Edworthy Audio Engineering Consultants 14

Where did we test trial loops?

   Ticket halls Walkways Platforms DGEA QT035_01 (c) Edworthy Audio Engineering Consultants 15

What did we find from the noise surveys?

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DGEA QT035_01 What did we find from the noise surveys?

 Most ticket halls and routeways, noise = unnoticeable or just noticeable  But some ‘hot spots’ close to equipment  Fluorescent lighting in low ceilings and in advertising displays  Electronic whiteboards used for public information displays and other ‘strobed LED’ signage  CRT visual display units at ticket windows (sound files are amplified – not the real sound level!) (c) Edworthy Audio Engineering Consultants 17

What did we find from the noise surveys?

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What did we find from the noise surveys?

 On platforms, magnetic noise from the traction supply and signalling equipment    Just noticeable in some locations to very severe interference in others The closer to the platform edge, the higher the level of magnetic noise Louder during the arrival and departure of trains  Announcements made during those times could suffer from poor intelligibility (c) Edworthy Audio Engineering Consultants DGEA QT035_01 19

What did we find from the noise surveys?

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DGEA QT035_01 What did we find from the noise surveys?

 At most help points and tube map locations magnetic noise would be unnoticeable or only just noticeable  But when a train arrives and leaves a station, there is significant interference at Help Points on platforms (c) Edworthy Audio Engineering Consultants 21

What did we find from the noise surveys?

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What did we find from the noise surveys?

 On escalators, very low magnetic noise  All-steel construction is good at shielding escalator motor magnetic noise DGEA QT035_01 (c) Edworthy Audio Engineering Consultants 23

DGEA QT035_01 What did we find from the test loops?

  Big variation between predicted and actual current needed  Bigger amplifier or complex loop antenna needed due to building construction metal Some locations caused significant reduction in high frequency performance of loop  More complex loop antenna configurations and/or specialised equipment needed (c) Edworthy Audio Engineering Consultants 24

DGEA QT035_01 The ‘Reality Check’   Q: Where would we expect a hearing aid user to switch the telecoil on?

A: Where there is an obvious benefit:     At ticket office windows At passenger help points At other places where signs show a loop is provided NOT everywhere in a Tube station (c) Edworthy Audio Engineering Consultants 25

What we recommended to London Underground DGEA QT035_01   Only install loops where users would expect them, and where the magnetic noise level is OK Remove/reduce the sources of noise    Replace CRT (tube) displays with LCD/LED Site passenger help points as far from the platform edge as possible Loop alternate ticket windows to avoid overspill from adjacent loops (c) Edworthy Audio Engineering Consultants 26

The solutions DGEA QT035_01    Most ticket windows have loops, and much less magnetic noise Most help points now have loops   Some variation in the type of loop antenna due to construction limitations Acceptable results in most places LUL ‘Manual of Good Practice’ for loops  Guides the design and installation of all new loops (c) Edworthy Audio Engineering Consultants 27

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The 21 st Century London Underground (The Tube) What Transport for London (TfL) wanted What we found in our survey of stations The ‘Reality Check’ The solutions (c) Edworthy Audio Engineering Consultants DGEA QT035_01 28

In conclusion    Thank you for listening!

Was it a good presentation for you?

   What went well?

What could have gone better?

What else do you want to know?

Feel free to contact me at [email protected]

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