[Bananensap]

I tested this:

#include <sdktools>
public OnPluginStart()
{
	AddNormalSoundHook(SoundHook);
}

public Action:SoundHook(clients[64], &numClients, String:sound[PLATFORM_MAX_PATH], &entity, &channel, &Float:volume, &level, &pitch, &flags)
{
	ReplyToCommand(0, sound);
	
	if (StrContains(sound, "sound_you_want_to_change.wav") > -1)
    {
		Format(sound, sizeof(sound), "directory/sound_you_want_to_replace_it_with.mp3");
		return Plugin_Changed;
    }
	return Plugin_Continue;
}

But weapon sounds are not catched in this event?
Only jump sounds etc.