Excessive Bass in the Audio (Part 2)
The key to solving the problem of too much perceived low frequency energy is to understand the source of the complaint. It is very likely from a consumer listening in surround via a home theater system. The area of the audio spectrum that is probably to blame is lower than many normal main channel speakers can reproduce, and it almost surely cannot be heard on a typical in-rack audio monitor of the type that many stations employ as a means of quality control just prior to transmission. Due to space limitations, it is also very possible that the low frequency energy may not be audible in master control, or in the case of live programs, it might not be audible even in the audio control area. Consumers that have surround systems also often have a subwoofer that by virtue of the large driver and special tuning is capable of reproducing some or all of this energy, depending on size.
Preventing complaints from viewers about excessive bass in transmitted audio can be accomplished in several ways. However, the most important thing is to ensure that somewhere in the facility there is a speaker system that is capable of similar or better performance than a consumer system. In fact, it is completely acceptable, perhaps even recommended to actually use a consumer speaker system for quality control of the final signal. The systems are comparatively inexpensive and when coupled with a video display can serve double duty in a conference room or lobby for showing off audio and picture quality.
Once proper monitoring is in place and properly aligned using at least an SPL meter or preferably an audio spectrum analyzer, judgment of low frequency performance can be ascertained. If live programming such as news is produced locally and is the cause of complaints, use of high-pass filters on open microphones is highly recommended--exact tuning will need to be determined on a case-by-case basis. If there is room noise from air handling equipment, this also needs to be corrected and will benefit from the same high-pass filtering. Having multiple microphones open on talent located close together can also cause an artificial boost in low frequency energy, and again filtering can help.
For programming that is delivered to a facility, there is little that can be done short of audio processing in the transmission path. Modern audio processing can dynamically control low frequency levels and will also usually contain filtering for all audio channels and is remarkably effective at inaudibly fixing these problems with minimal impact to other audio.
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