Have you tried asking the EHO to stay the night with you and listen then
On a lighter note though at least he could hear the humming. Its back to the EHO.
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local