The wait is over ...
In September 2007 I received a mail informing me about a particularly wonderful Chinglish File in Guangzhous's Martyr's Park 广州起义烈士陵园 (see Wikipedia entry) and immediately called for photographic support.
My call was answered yesterday.
喧哗 xuan1hua2 - actually can mean whoopla or hullabaloo, no doubt about that. Here it rather indicates to keep your voices down. I hesitate to suggest "Silence, please" as an alternative translation，however, since this is usually used in museums or cemeteries, not in parks. What do you think?
Many thanks to Phillip!