Scott, yes, I would suggest you mix the sound unit in with the drive motor ESC throttle channel, and not with the hydraulic valve channels. The 1:1 wheel loaders have a foot throttle and a good operator will lift off the throttle completely, and wait until the machine is at a complete, or near stop before changing directions. It might be misleading to think the operator is on the throttle to speed up the hydraulic pump for lifting or steering, when in fact that is simply the torque converter slipping, while the engine RPMs come back up. Depending on what gear the operator is in, there might be more, or less lag, from the point when you hear the engine rev and to the point that translates into the wheels turning.
The hydraulic pumps still put out good flow at idle, so the bucket will lift and the loader will steer just fine (although a bit slower at that point), when the operator is off the throttle, but when you watch a wheel loader at work, there really isn't much time that the engine isn't running at a higher speed, except for when the machine comes to a complete stop. At that point, the loss of bucket cycle speed is minimal, especially considering the operator will be back on the throttle very soon. When dumping a full bucket at stop (bucket already raised up), not a lot of flow is needed to tip the weight. Bucket 'dig in', is usually done under power, as the operator is pushing pretty hard into the pile, with the engine RPMs up, even if the wheels aren't spinning. The torque converter may be slipping at that point, especially in the higher gears. Efficient operators will already have the bucket raised by the time they get to the truck, while the machine is backing away from the pile, changing directions, and then approaching the truck; engine running at elevated throttle through that process. So I've not known any operators to rev the engine while cycling the bucket with the machine at a stop, unless they are lifting something so heavy that the hydraulic pump can't put out enough pressure or flow to raise the weight.
I know this is long winded, and I apologize, but long story short, I would not tie the hydraulic valve channels into the sound unit for this reason.
