The first phase of the transformation of South Bank Centre is underway and by 2007 the Royal Festival Hall should have London's most flexible concert acoustics.
The task of enhancing the acoustic has been entrusted to Larry Kirkegaard and his Chicago firm Kirkegaard Associates.
The Hall was built for the 1951 Festival of Britain with two 12 inch concrete walls on the south side to keep out the noise of the railway. Further reducing background noise to near silent levels will now involve eliminating air condition sound
The roof will be rebuilt to the thickness originally intended to reflect sound back to the orchestra and avoid complaints from players struggling to hear their sound.
Because orchestras have grown in size since 1951 it has been decided that the stage must be enlarged. The famous organ will be moved back a few feet.
The auditorium's 2,900 seats, designed over fifty years ago by Robin Day, will be recovered in material sympathetic to the original colour concept. Carpets will be removed as part of the drive to improve the depth of sound.
"The refurbishment of the Festival Hall will allow audiences to experience its rich programme in an environment and an acoustic that matches the quality of its performers" says David Whelton, the Philharmonia Orchestra's managing director.
SBC chief executive Michael Lynch, who claims that London is the most competitive town musically, says: "The acoustic aspirations of the original designers were never fully realised. Now we have the opportunity to complete the job".
• The Royal Festival Hall is due to close for 18 months from next July.