Scenario 4 – Auditory Sensitivity in Factory Workers

Factory workers operating in a very noisy environment are at risk of developing hearing problems; this necessitates regular hearing checks. Part of your role is to measure the absolute threshold of hearing to ensure that there are no auditory problems developing. Your test involves presenting a 30Hz tone at several levels of loudness (dB level) and determining whether they heard the tone or not. You adopt the Method of Constant Stimuli, presenting the different loudness levels 12 times each.

The first worker you see had only just joined the factory and presented with the following results:

Loudness of the 30Hz tone (dB)	5	10	15	20	25	30	35	40	45
% yes (heard) responses	0.08	0.16	0.28	0.44	0.6	0.76	0.88	0.96	1.0

The second worker was older and had been working at the factory for nearly twenty years. You measured their hearing using the same approach and recorded the following responses:

Loudness of the 30Hz tone (dB)	5	10	15	20	25	30	35	40	45
% yes (heard) responses	0.04	0.08	0.08	0.19	0.4	0.53	0.76	0.97	1.0

On the same graph, plot a psychometric function of the hearing data for both factory workers.

Using the graph, estimate the absolute thresholds of hearing for both factory workers.

Based on your findings, which factory worker has the more sensitive hearing? Provide a brief explanation of your decision.

How many trials are presented to calculate the threshold using this approach?

You have been asked to develop a new test that will provide you with a threshold estimate but will not take as long as the current method. Outline an approach that you might adopt giving a reason for your choice.