my wall mounted show 15 makes a faint but constant high-pitched buzzing or whining noise from the back.

Diagnosis

The high-pitched whining noise emanating from your Echo Show 15 is a phenomenon known as "coil whine." This occurs when electronic components—specifically the inductors and capacitors within the DC-DC voltage converter on the main logic board—vibrate at a frequency audible to humans. Because the Echo Show 15 has a high power draw (30W) to support its large 15.6-inch display and integrated speakers, the power circuitry is under constant load, which can trigger these vibrations. The issue is significantly amplified by the wall-mount installation. When the device is flush against a drywall surface, the wall acts as a physical sounding board, resonating the high-frequency vibrations and projecting them into the room. You can confirm this is coil whine by moving the device away from the wall; if the noise persists but becomes quieter or changes pitch when you change the screen brightness or trigger a voice command, it is definitely electronic resonance rather than a mechanical fan failure (as the Show 15 is passively cooled).

How to Fix It

To mitigate the noise, you must address the stability of the power delivery and the physical coupling between the device and the wall. Follow these steps precisely:

1. Power Cycle and Reseat: Completely unplug the 30W power adapter from the wall outlet and the USB-C port on the back of the device. Wait 60 seconds to allow the capacitors to fully discharge. Reinsert the cable firmly, ensuring the connector is seated deep into the port with no gap.
2. Isolate the Power Source: Plug the adapter directly into a wall outlet rather than a power strip or surge protector. Cheap surge protectors can introduce "dirty power" or electrical noise that exacerbates inductor vibration. If possible, test the device on a different electrical circuit in your home to rule out line noise.
3. Adjust Display Settings: Go to Settings > Display and turn off "Adaptive Brightness." Manually set the brightness to a mid-range level (around 50%). Extreme brightness levels increase the current draw through the DC-DC converters, which often increases the intensity of the whine.
4. Introduce a Vibration Buffer: If the noise is resonating through the wall, place small, adhesive rubber bumpers (3mm thick) between the back of the Echo Show 15 and the wall mount. This breaks the physical bridge that allows the wall to act as a speaker for the electronic noise.

If That Didn't Work

If the buzzing persists after the steps above, try these deeper troubleshooting methods:

• Swap the Power Adapter: While it is tempting to use any USB-C charger, the Show 15 requires a specific 30W delivery profile. If you have another official Amazon 30W adapter from a similar device, swap them. A failing capacitor in the external brick can send unstable voltage to the device, triggering the internal coils to whine.
• Toggle the "Night Mode" Schedule: Set a strict Night Mode schedule in the device settings. This reduces the power state of the screen and processor during specific hours. If the noise disappears during Night Mode, the issue is tied to the power load of the display panel.
• Check for Interference: Ensure the power cable is not bundled tightly with other high-voltage cables (like HDMI or thick power cords for a TV). Electromagnetic interference (EMI) can sometimes induce a hum or whine in the unshielded portions of the power circuitry.
• Request a Hardware Replacement: Because coil whine is a physical property of the inductor's winding, it cannot be fixed via software. If the noise is audible from more than three feet away, it indicates a component that is out of tolerance. Contact support for a replacement unit, as some batches have higher tolerances for coil whine than others.

Heads Up

• Avoid Third-Party Cables: Never use a generic USB-C cable to power the Show 15; the gauge of the wire in cheap cables causes voltage drops that force the internal regulators to work harder, increasing the likelihood of whining.
• Ventilation Matters: Ensure the wall mount is installed correctly and not pressing the device so hard against the wall that it traps heat. Overheating can change the physical properties of the capacitors, potentially worsening the noise.
• Firmware Updates: Keep your device updated. While coil whine is hardware-based, Amazon occasionally releases power-management firmware updates that optimize how the CPU handles voltage, which can subtly reduce the noise.