I have not tried disconnecting the speaker. I will give it a try.
Thanks for the suggestion, Joe.

-Vefa

Thanks for your response.

Few clarifications: This loco came with the sound decoder and the speaker factory-installed. So I am assuming they are installed correctly. The speaker is facing upward in the tender and seems to be using the baffle kit from soundtraxx:
http://www.sodigi.com/Enc_Shay.jpg


The buzzing is loud even with the sound turned off, and changes frequency with the speed, so it is definitely the decoder. I have other locos with decoders and none of them has any buzzing this extreme.

I have recently purchased the HO 3-truck shay. I must say the details and the looks of this little engine is impressive. However the Soundtraxxx LC decoder and the measly speaker that Bachmann decided to include in this loco does not do justice to this otherwise excellent engine. The cheap sound decoder and the speaker ruin everything, making the engine sound like a cheap toy.

The decoder buzzes so loudly, especially at low speeds that the noise exceeds the actual chuffing sound coming from the speaker.  I have changed the CV setting that adjusts the frequency (PWM) and set it to the highest, to no avail.  I have also set the sounds to the max, which actually made the sound quality even worse. 

Just for testing, I have replaced the Soundtraxx LC on the shay with a LokPilot Basic decoder from one of my engines. The difference was very clear and immediate: Although the engine jerked a bit at very low speeds, there was no buzzing at all.

Here is what was advertised for this sound decoder and what I got:

• authentic sound effects uniquely appropriate to each model including whistles, bells, chuffs, and air pumps
• additional sounds include dynamo, injectors, coupler clank, water stop and more --> These  are not included in this decoder
• three whistles to choose from in each model
• whistle can be played in real time to create authentic whistle signals
• high quality 16-bit digital sound --> It is definitely not high quality, or at least not apparent with the weak speaker
• advanced motor control features including Load Compensation and Silent Drive to provide smooth, quiet operation --> It is neither smooth nor silent, buzzing noise is unacceptable
• supports all recognized programming methods

I do not understand why Bachmann would let this go through their QA department. Was the decoder buzzing level  acceptable to them? Don't they test every engine they manufacture?

What are my options at this point? Get rid of the LC decoder and get a decent one? Other alternatives?

Thanks for listening.

-Vefa