TrueRTA is a collection of real-time software-based instruments for testing and evaluating audio systems using a PC with basic sound input/output capability. The instruments found in it include a low distortion signal generator, a digital level meter, a crest factor meter, a dual trace oscilloscope and a high-resolution real time analyzer. By creating these test instruments in software and employing the signal input and output capability of your PC's sound card, we are able to offer a level of performance that could only be achieved by many thousands of dollars worth of traditional test instruments. In combination with your PC, TrueRTA provides a powerful audio testing capability, normally seen only in better audio research and design laboratories. The figure below shows TrueRTA measuring the sine wave performance of the internal digital signal path of a PC. Note that in this measurement all harmonics of the test tone are more than 80 dB below the test signal (0 dBu). This indicates a distortion level below .01%.
The default input sampling frequency for TrueRTA is 44.1 kHz, the CD sampling frequency. Increasing the sampling frequency to 48 kHz or 96 kHz will increase the high frequency measurement bandwidth but will also reduce the low frequency resolution. So the best overall tradeoff for many audio measurements will be the default 44.1 kHz.
TrueRTA will remember your sampling frequency settings from session to session. If you need very high resolution in the lowest octaves you may want to set the sampling frequency lower in order to increase resolution in the very low frequency range. The choices of input sampling frequencies are: 8, 11.025, 16, 22.05, 24, 32, 44.1, 48 and 96 kHz. The 96 kHz sampling frequency works with some sound cards to extend TrueRTA's measurement capability to 48 kHz.
The output sampling frequency is selectable between 44.1, 48, and 96 kHz. Normally you will leave this set to 48 kHz. The 44.1 kHz output sampling frequency is only provided to assure compatibility with the widest possible range of sound cards. In order to perform measurements to 48 kHz you should set both the input and output sampling frequencies to 96 kHz.
The license of this software is Free Trial Software, the price is $39.95, you can free download and get a free trial.