Application description guide

Introduction

MkAudiogram is a hearing test where a user can hear a sequence of pure tones ranging from low to high frequency, as in a musical scale say, and make volume adjustments until the sequence is perceived to be of consistent volume. This contrasts with the usual practice where tones are played at different frequencies and reduced in volume until they become inaudible. It must be stated that MkAudiogram is not intended to be a substitute for the official method but rather an additional aid which is likely to appeal to musicians and music lovers.

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Some essential basics that you need to know

As MkAudiogram is only intended to provide a basic hearing test it uses the Web audio oscillators to produce the sound tones rather than some high fidelity mechanism. The volume output from an oscillator is controlled by its gain value which can only vary from 0.0 (muted) to 1.0 (maximum volume), where maximum volume equates to the current volume set by the output device. So in essence the output device has to be set loud enough to accommodate the largest correction, which is likely to be at some high frequency level, and yet still be audible at a much reduced volume at the lower frequencies that are deemed to require no correction. This has consequences that depend on the output device, the severity of the users hearing disability and the reason for taking the test. Consider the following possibilities:

No obvious hearing problem but just curious, then set the frequency to its maximum (index 84), set the step control to 1 semitone, select mono output and set output device volume to be normal; then click play to hear the full range.

You have a hearing problem but as yet no aids and would like a result which could be helpful to an audiologist. In this case be aware that the highest correction point of a hearing aid is about 8kHz or possibly 10kHz. If a large correction looks to be necessary a rescaling of the volume slider fields will be required. A direct way of achieving this is as follows: start from the initial state and set select mode on, select the highest frequency and set its volume correction to its highest. Then increase the volume of the output device so that the tone becomes audible. If this is unachievable move down the frequencies until you reach one that is audible. Now select a tone at the lowest frequency and reduce its volume until it is a good match for the upper note. Finally, with just the two selected, click [rescale] to rescale the volume sliders and the lower tone will be at the 100% level, i.e. the zero correction level. You are now setup to make adjustments over the whole range as outlined in the hints and good practice section to produce an audiogram which may be of some use when you go for a professional test. Note that presented as just a guide it need not be complete or higly accurate. Health warning: setting the output device to its highest volume could be problematic for your hearing health so proceed with care.

You already have and use hearing aids which to some extent do the job but could be improved. Usually the problem is that the aids have been set for improving conversation, the top frequencies are over compensated and not suitable for appreciating music. In this case the corrections are likely to be to decrease the volume and the only change to the slider range will be to reset its minimum to a lower value.

Hearing aids with no bluetooth compatibily The question here is what is the most suitable output device and how to affectively isolate one ear bearing in mind that headphones are not the answer.

Hearing aids with bluetooth compatibily This is the ideal case provided the sound output can be established as a bluetooth signal. The simplest case case is when the host computer and the hearing aids are bluetooth compatible. Failing that, a bluetooth TV streamer plugged into the computer's headphone output socket gives good results.

A lot depends on the quality of the computer's audio system and it is crucial the computer's oscillators used by MkAudiogram produce sound sequences of equal volume. If your own hearing is poor it is strongly recommended that you get someone with good hearing to check out that a full sequence played at the base volume sounds consistent. Warning: be aware that the oscillator can over emphasize the initial note played of a selected sequence.

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The basic and active sets

The end product of MkAudiogram will be two basic sets of volume corrections, one for the left ear and the other for the right ear. These will be expressed as percentages to be applied to some fixed volume level, i.e. a 50% correction requires the volume to be halved and 200% it to be doubled. The third basic component is a set of frequencies of semitones ranging from index[1] 130.8 Hz to index[83] 15804Hz and is constant and cannot be changed. On entry to each new test session the volume corrections are all set to 100%, i.e. the no correction required. The save, restore and archive options can be used to save the basic set across sessions.

The active set is a subset taken from the basic set and is the subject of the current test. Its range can be established by using the control options to set the indexes of its first and last members and the stepping option to step in 1, 2, 3, up to 9 semitone intervals. The active set acts as a kind of window into the basic set so that volume correction changes are made directly to the basic set. The current active set is always visible in the frequency table.

The selection set is a temporary subset of the active set. First turn selection mode on, then create the selection by clicking on the rightmost entries in the frequency table. The selection can then be played either, by double clicking any one of the selected butttons or by using one of the two play buttons. The double click mode can optionally be disabled. The selection is always sorted and played from low to high. Note: selection mode is switched off automatically when a change that causes the frequency table to be redisplayed.

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The frequency table

The frequency table displays the current active set of note frequencies and volume corrections. The columns are:

1. the entry's index,
2. the name of the note (A = 440 tuning),
3. the note's frequency value in Hz,
4. becomes activated as each note is sounded,
5. the percentage correction applied to the base volume,
6. the slider form of the correction applied to base volume,
7. select entry by clicking when in selection mode.

Columns 5 and 6 are closely tied giving the option of using column 6 for large changes and column 5 for fine adjustments. Note: the slider control only responds to mouse clicks and column 5 can be either set manually or by using its built in control.

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Note duration

The note duration time affects the apparent speed of delivery. A small value of about half a second produces a fairly rapid sequence of sounds perhaps suitable for an initial test in to order to detect general problem areas. Set a longer duration, around two seconds say, for a more focused inspection particularly when working on a small selection.

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The oscillators wave form

The oscillators can be established to one of four digitized styles, all of low quality. Check them out and select the one you think is the best suited for the purpose. Note that only the sine wave form is pure and the others may generate additional partial frequencies.

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Synchronous and asynchronous methods

The asynchronous method is one of two methods of generating the note sequence and does it by setting it to proceed automatically at predetermined time intervals as a background task which once started cannot be stopped. In this case the sound indicator has to be matched independently and can sometimes appear slightly off. On the other hand the synchronous method plays each note in response to the event of the previous note ending. The sequence can be stopped at any time and is also matched accurately with sound indicator. This is the default method but unfortunately it is more susceptible processing conflicts that can cause the browser to crash. To avoid these you are advised to always let the sequence run its course before attempting any changes.

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Managing the output

The default output type for play back is auto which outputs to the single stereo channel appropriate for the ear setting. If the sound separation is being performed externally a more basic approach would be to simply output mono. The third option, which could be useful at the final stages of a test, is to output stereo with the appropriate channels carrying the left and right ear results.

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Saving and restoring the current state

The current state can be saved to local storage and later restored to continue the test. Note: the save and restore buttons briefly change to [done] to indicate that the action is completed then automatically change back to [save] and [restore]. The state is saved in the form of a Javascript text file and its location is not normally known except that it will be in the user's storage space. Therefore it can be assumed to be safe from being overwritten on a shared computer provided the user name is not shared.

Archiving the volume corrections

You can archive up to ten sets of volume corrections where each set includes the properties:

1. identification label: mkarch1, mkarch2,..,mkarch10,
2. the date of the last action,
3. the type, i.e. left, right or both volume corrections,
4. your descriptive comment
5. one or both complete sets of the basic volume corrections.

Saving to an existing entry performs a merge operation depending on types i.e. saving the left set to a right set entry results in a both sets entry. A save operation always sets the date field to the current date. The archive is stored on the host computer as described for the save and restore options and cannot be exported and its lifetime over long periods cannot be garranteed.

Clearing the storage archive The archive has a capacity to save and restore up to 10 entries and given you can also overwrite existing entries it can maintain an indefinite service. On rare occasions when there is a need to reset all entries to be unset click here

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Creating and printing a results chart

A chart showing the test results in graphical form can be displayed by clicking the [show] button placed directly under the frequency table. The only option of getting a printout of the test results is to export the chart as an image file which can then be displayed and sent to a printer.

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Help mode

You can turn on Help mode to get help popups which can be displayed by hovering the mouse pointer over an input item. In the case of groups of related items, hover over the leftmost item or to get help on table column items hover over the column headings. Although usually normal use is unaffected it is advised that when done you switch help mode off for improved efficiency.