data = data_sabin2005

`data_sabin2005` returns percentage of quasi-veridical responses
(audible and within 45 deg of the regression line) as a function of
sensation level averaged across all listeners.

The `data` struct comprises the following fields:

'gain' |
gain of regression line. Field f
for frontal targets, field r for rear targets. Field
m for across-listener means, field sd for standard
deviation across listeners |

'pqv' |
percent quasi-veridical responses (within +-45 deg relative to regression line. Fields as for gain. |

'var' |
standard deviation of quasi-veridical responses from regression line . Fields as for gain. |

'SL' |
sensation level in dB (re audibility threshold) |

A. T. Sabin, E. A. Macpherson, and J. C. Middlebrooks.
Human sound localization at near-threshold levels.
*Hearing Research*, 199:124--134, 2005.