[Harp-L] Comb Debate

[Vern]

When hearing or playing a set of harmonicas, people do subjectively hear differences.  In previous tests many people perceived differences when the same comb material in the same harmonica was  played multiple times.  The question “Did you hear differences?” will most often be answered “Yes.” However, this doesn’t answer the question “Did the materials perceptibly affect the sounds?" 

An experiment to determine this real question must be carefully designed.  This is not an easy task.  It requires careful preparation and a rigorous procedure.  In the case of testing people’s ability to hear comb-material differences, The following are requirements:

- The test must be blind.  The listeners and players must have no knowledge of what material is being played.
- Extraneous variables must be eliminated or suppressed to the extent possible. Using one set of plates and covers is good practice.
- There must be a statistically valid number of samples.  About 50 for two materials is recommended.  This makes the test long and boring for both spectators and participants.
- The sequence of materials played must be random.
- The participants must record their perceptions and hand them in for scoring before the material sequence is revealed.
- The scoring method must be determined and written down before the test starts.

For more on design of experiments, see https://en.wikipedia.org/wiki/Design_of_experiments <https://en.wikipedia.org/wiki/Design_of_experiments>

Changing inserts in the same ACE48 would greatly facilitate such an experiment if the other requirements are met.

Finding even one person who could reliably identify comb materials by playing or hearing the harmonicas under such controlled conditions would confirm a materials effect. So far, that hasn’t happened.

Vern

>> On Jul 25, 2017, at 8:46 PM, Tom Halchak <info at xxxxx> wrote:
>> 
>> I have a simple question for everyone.
>> 
>> When was the last time you had the opportunity to play five identical
>> harmonicas with the only difference being the material out of which the
>> comb was constructed?  ………….
>> 
>> ………...At The Great Comb Debate Workshop at SPAH 2013, I prepared not five
>> identical harps with different combs.  I prepared 20 brand new harps with
>> different combs…………
>> 
>> …………...At the end of the workshop we had a contest to see who could correctly
>> identify the most harps as they were played from behind a curtain out of
>> view.  Truthfully the scores were not that high.  Margie Goldsmith won The
>> Golden Ear Award for the highest score………...I