Dear Robert,
There are many free wares are available for this purpose. But the excellent commercial one would be "Audobe Audition" That costs you 299USD.
You can also have a look at speech perception lab wesite of university os Nabraska. It has many good softwares which you can down load freely. http://hush.unl.edu/LabResources.html
You can also try Test tone generator and Multi tone generator at http://www.esser.u-net.com/ttg.htm. These are trial versions fo 30 days. But after expiration you can reinstall it.
All the best
Ajith