Scientific articles on piano acoustics describing more recent findings can be found in the international acoustic journals. In particular, see
The Journal of the Acoustical Society of America
http://asa.aip.org/map_publications.htm
Acustica - acta acustica
http://www.icp.inpg.fr/ACTA/
Royal Institute of Technology:
Department of Speech Communication
http://www.speech.kth.se/
Music Acoustics Group
http://www.speech.kth.se/music/
Royal Swedish Academy of Music:
http://www.musakad.se/
Swedish Piano Tuners and Technicians Association:
English: http://www.sptf.com/index_english.html
Swedish: http://www.sptf.com
One of the most extensive collection of links related to the piano is found at:
PTG - Piano Technicians Guild: http://www.ptg.org
This page is a part of Five lectures on the Acoustics of the piano