As in the subject, the sound of spam clicking on a locked slot is unbearable! :)
At least on this version what I am: 1.8.8

EnderChestHubMenu
MiscUtil.playSound(player, "ANVIL_BREAK", "BLOCK_ANVIL_BREAK");

I had to exchange it for
MiscUtil.playSound(player, "GLASS", "GLASS");

I know that is:

    private static Sound generateSound(String sound18, String sound19) {
        Sound sound;

        if (MiscUtil.soundExists(sound18))
            sound = Sound.valueOf(sound18);   // 1.8
        else if (MiscUtil.soundExists(sound19))
            sound = Sound.valueOf(sound19);   // 1.9+
        else
            return null;                      // Else? Not supported.

        return sound;
    }

But it's loud and unpleasant

Yes I agree with you. To be honest I don't even remember why I have chosen the sound of an anvil when a player can't access to an enderchest. I will change that!

Hello @radek203, I have changed the sound played when a player cannot access its enderchest in the commit 31d18b4. I used the sound VILLAGER_NO because it fits well with the situation. Is it OK for you?

Now is good! :)