Richness (ri) option is similar to smoothness and brilliance except that the spectral change occurs at lower frequencies and is because of a different physiological mechanism. Brilliant, rich voices carry well and are more intelligible in noisy environments, while smooth, soft voices sound more friendly. For example, the following command produces a soft, smooth version of Paul's voice:
[:np][:dv ri 0 sm 70] Do I sound more mellow?
The following command produces a maximally rich and brilliant (forceful) voice:
[:np][:dv ri 90 sm 0] Do I sound more forceful?
Smoothness and richness are usually negatively correlated when a speaker dynamically changes laryngeal output. The sm and ri options do not influence the speaker's identity very much.