What Is HD Audio?
You have heard of HDTV, and maybe HD Radio, but what do we mean by HD Audio? Well, let me use HDTV as a way to explain HD Audio. Compared to SD (standard definition) , HDTV is really two things: first, its digital. Second, it supports a higher resolution than traditional analog televisions.
Video resolution is based on the total number of pixels, or the number of samples that make up an individual video frame. Its also based on how often those pixels are refreshed. A typical 1080p HDTV has 2,073,600 (1920 x 1080) pixels refreshed 60 times per second (or Hertz, Hz). Some TV’s offer 120 Hz or 240 Hz refresh rates.
In contrast, a 480i standard definition TV has only 345,600 (720x480) pixels, refreshed 30 times a second; only 1/6 of the pixels that HDTV offers.
Standard audio operates at the following sample rates:
8k samples per second (Telephone, similar to AM Radio)
32k samples per second (Net audio, similar to Cassette Tape, FM Radio)
44.1k samples per second (Standard Compact Disc)
48k samples per second (DAT, HD-SDI, Digital TV, DVD, some Blu-ray)
HD Audio starts with all of the above formats and adds 96k samples per second, a rate that is used by professional studios, in films using Dolby, and DTS, and for audiophile recordings on SACD (DSD), and DVD-Audio. The higher sample rates are needed to reproduce timbre, as some people claim they can hear the difference between triangle and sine waves at barely audible frequencies. Also, the higher the sample rate, the more effective the Nyquist filters can be.
WiSA testing ensures that every WiSA compliant home theater system operates without degrading the quality promised by the source material. By using the same sample rate as the original content being played on the television, there is no audio loss because of extra conversions (downsampling or up-sampling). The frequency range is limited only to the original sampling rate. The transmitted audio is not compressed. (Compression could cause scratchiness, buzzing, ’robot’ sound, or other artifacts in varying degrees.)
For most people, the range of human hearing is about 20 Hz to 20,000 Hz (20 kHz). The exact range depends on the age of the person, as our hearing tends to degrade over time. The human frequency response is often a topic debated among audiophiles; many believe the subsonic and supersonic frequencies are still adding to their overall experience. Is it possible that body parts that can hear certain frequencies that the ear can not detect? We welcome your input.
