This is one of the cheapest tools you might buy with a fair selection in the $4-$10 range. Harbor Freight sells them downright cheap. Make like a doctor, plug it in your ears, and touch the metal tip wherever you want to listen. Beware the odd noises you search may be quite loud. Ticking tappets suddenly sound like hammering on a bucket, and a bad ball bearing may sound like a chain saw. The keen advantage to this tool is being able to pick up local noises wherever you touch the tip of the tool. You can easily tell the difference between a water pump bearing and a generator bearing, and you can tell which tappet ticks louder than others.