A complaint that has arisen of late demonstrates one of the challenges a digital transmission path that is capable of reproducing the entire audio spectrum. In the past, frequency response was in many cases limited from 50 Hz to 15 kHz, usually with an emphasis on the midrange for intelligibility through somewhat less-than-ideal speakers. This was often accomplished through built-in filters in the audio processing. The 15 kHz upper limit is part of the NTSC audio standard and is a nonbypassable feature of that system. The lower frequency limit is more self-imposed by broadcasters to prevent transmission of modulation robbing sub-sonic information.
The ATSC system by virtue of the Dolby Digital (AC-3) system described in A/52 provides an escape from these limitations by offering the capability of full frequency response audio from 20 Hz (or lower) to 20 kHz from the broadcaster to the consumer. In cases where broadcasters do not employ any broadcast audio processing prior to encoding, or have broadcast processing misadjusted, sub- or infra-sonic energy can now be sent directly to consumers. Depending on their speaker setup, bass management may very likely be employed to allow small satellite speakers to be used for the main channels and a subwoofer to be used to reproduce both the LFE channel and the low frequencies from all of the satellites. If all is adjusted properly, there may be little trouble. However, as anecdotal information has shown, in many cases consumer subwoofers are set too loud.
All of this combines and can result in complaints of excessive bass, even on the voices of newscasters. The luxury of being able to rely on the old analog standard and its support gear to filter out these problems is gone. Broadcasters once again must remain keenly aware of the benefits and challenges of having more audio performance than ever before.
