Most people acquiring hearing aids report trouble hearing speech, or more often trouble hearing speech in noise. Here speech testing becomes a strong test tool in the assessment of the problem the patient faces. Speech audiometry employs speech signals and can be used to examine the processing ability and if it is affected by disorders of the middle ear, cochlea, auditory nerve, brainstem pathway, and auditory centers of the cortex.
There is a variety of tests available with speech testing with the basic speech audiometry being an assessment of the reception, discrimination, and recognition of speech. Reception refers to the level at which the patient can hear speech is present, discrimination refers to the level at which the patient can discriminate between words, while recognition refers to the level at which the patient can recognize and recall the word.
Speech Detection Threshold (SDT)
Speech detection threshold (SDT) refers to the level at which the patient can hear speech is present in 50% of the cases.
The speech detection threshold can be used as a cross-check of the air conduction audiometry and should closely agree with the PTA (Pure Tone Average). The PTA can be calculated in different ways but is usually the average of thresholds obtained at 500, 1000, and 2000 Hz. It is generally accepted that if the PTA and the SRT are within ± 6 dB of each other the accordance is good, if it is ±7 to 12 dB it is adequate, and if it is ±13 or more, it is poor.
Note: Speech detection threshold is sometimes referred to as speech reception threshold abbreviated – SRT, not to be confused with speech recognition threshold, abbreviated – SRT. For that matter, the term speech detection threshold is used and abbreviated – SDT.
Speech Recognition Threshold (SRT)
The SRT examines at which level 50% of the speech material (usually numbers or spondaic words) is repeated correctly.
In addition, SRT gives an index of the hearing sensitivity of speech and helps determine the starting point for other supra-threshold measures such as WR (Word Recognition).
