Hello Oren, Assuming the replacement felt was installed and regulated properly there are a couple of issues that may be of help. The damper may not have enough mass to work well. Consider trying to install some brass or lead weights to the head to see if that helps. Often, in older pianos, the felt was too short to do the work required of it. I would ask your technician to consider installing longer felts to see if this will help. DO make sure the string braiding is in place all through the piano, bottom to top. Sometimes sound get get into the corners of the soundboard, upper left and lower right corners over which the damper has no effect. There should be blocking or no board at all in those areas. If those areas have not been isolated from the main part of the board there is little that can be done about it at this stage. Perhaps you would prefer to get another technician's opinion as to the source of the problem and it's solution. Bear in mind that a certain amount of "echo" is inherent in most upright pianos because the dampers are not located in the optimum place which is where the hammer will want to hit the strings. Upright damper location is a compromise. I wish you lock. Newton
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