Creating a system you love shouldn't be difficult. The Acoustic Frontiers blog is here to help.
Hum and buzz in audio systems and home theaters
by ct_acoustic_frontierJuly 06, 2022
What effect does 'hum' and 'buzz' have?
'Hum' and 'buzz' can cause major noise issues with our high performance audiovisual systems.
Hum is a superposition of the 60Hz mains AC frequency on the audio or video signal.
Buzz is a superposition of the harmonics of the 60Hz (120Hz, 180Hz, etc) mains AC frequency on the audio or video signal.
How is hum and buzz caused?
There are three main mechanisms that cause hum and buzz:
Interchassis currents between pieces of equipment with OR without a saftey ground as a result of 'stray' capacitance in the power supply
Ground loops - more specifically differences in the voltage of the safety ground wire between interconnected equipment
Electromagnetic coupling of AC and signal cables
For a more detailed discussion we suggest reading the Jensen Transformers guides below.
How do I solve hum and buzz?
A common root cause of hum issues are ground loops caused by equipment being on different electrical circuits or being plugged into different outlets on the same electrical circuit. The solution to this is to use good grounding practices - i.e. having a single grounding point for equipment and connecting all equipment to this with short, high gauge (low impedance) power leads. Powerbridges (in wall electrical circuits that are not always connected to the home electrical system; they are essentially normally de-energized electrical circuits that are energized when one end is plugged into the outlet of a power conditioner or UPS) can be used for subwoofer and projector in wall runs.
In most other cases the root cause of hum and buzz can be tracked down to a single interface between two pieces of equipment. We suggest using the Isomax Troubleshooting Guide to identify the root cause of the hum and buzz issue. The solution is generally to isolate the two components as follows:
Much confusion still exists about what a room correction product does, what problems it can (and cannot) solve and therefore its 'place' in a modern high quality sound reproduction system. Part of the challenge of understanding room correction is that it requires a reasonable level of understanding of sound quality, acoustic science, acoustic measurement and psychoacoustics (how humans perceive sound). The majority of the articles I have read online or in print magazines do not cover the fundamentals in enough depth to allow the curious and committed reader a chance to understand room correction on anything more than a cursory level. By the end of this article I hope that you will have learnt enough to judge for yourself what room correction can and cannot do and how best to apply it in the context of a world class music or home theater system.