Sound Replacement Problem

I have the Beta Gravity Gun launching sound as a .wav file. So I was going to replace the original sound of the gravity gun with this one. I made a folder called sounds, then made a folder in that one called weapons, then physcannon in that one and put the .wav file in it. I put it in C:/Program Files/Steam/steamapps/youaccountname/half-life 2/hl2. I pasted the sounds folder in there and it woun’t use that sound in-game. Any help here would be great.

It needs to have the exact same filename as the one it replaces.

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