Categorization of PSAPs?

Wayne Staab
August 8, 2017

This post is a continuation of two previous posts relating to a proposed PSAP “Standard” (OTC Hearing Aid Standard, and PSAP Standard Review).  This post relates to a section of the proposed “Standard” relating to the “categorization of PSAPs” (personal sound amplification products).1  


Categorization – Criteria for Standardization

It is not clear what the purpose is for categories of device performance.  Is the intent that a PSAP would have different levels of performance and labeled as Category 1, Category 2, or Category 3?  Is a PSAP a PSAP or not?  This suggests different levels for PSAPs.  Since there is no such categorization of hearing aids, then why for PSAPs?  With these thoughts in mind, the following is a continuation of attempting to determine what the various parts of the “Standard” relate to, and how they may or may not be significant.


Category I

This category is proposed to provide an acceptable range or threshold for the measurement made.  Acceptable to who – the consumer or to those writing the” Standard?”  On what basis is acceptability determined?  It is possible that a $29 unit may be just as acceptable to one person as a $3000 unit is to another person?  In speaking to a friend the other day, he commented that his dad purchased a $29 unit to help his hearing.  I asked how he was doing, and was he satisfied?  I was told that he is doing acceptably well, and that he was pleased with his purchase.  Just because a measurement meets the “Standard” says nothing about how acceptable a product is to the consumer.  Meeting or failing a single feature reminds one of something J. Donald Harris wrote about many years ago (paraphrased): just because you can find a single parameter statistically significant when viewed in isolation, it may have no significance when all parameters are combined.


4.1 Frequency Response Bandwidth

Figure 1.  Three different premium-priced hearing aids measured using a 2cc coupler and an open fit coupler (Frye Electronics open coupler).  How does making the measurement of a PSAP having an open fit on a 2cc coupler aid the consumer, since the responses (including the bandwidth), will be substantially different?

How does a frequency response allow a consumer a means to compare and evaluate competing systems?  The same response fitted with an open or closed dome (Figure 1) provides different end user real-ear listening experiences.  Even premium-priced hearing aids do not provide this real-ear information to the consumer.  It is suspected that few hearing aid or PSAP consumers even know what a frequency response curve is, or what it actually represents.  The “Standard” calls for measurements to be made into a 2cc coupler.  However, many PSAP instruments are sold only with an open fitting, not a closed fitting, as is measured in a 2cc coupler.  Therefore, it is confusing as to why they would be measured with a closed coupler, and then this information provided to a consumer, when it has nothing to do with the actual frequency response representation.

Figure 2.  Three premium hearing aid manufacturers’ published frequency response lower and upper limits, and actual measured responses (measured in 2016).  None met the upper limit, which most would agree is a more significant number than the lower limit.  The “Program” is the measured response after each was programmed to the same hearing thresholds.  The MZ-1 is a modified Zwislocki coupler measurement.

If truth in advertising, especially with respect to the frequency range is so important, current premium-priced hearing aids (among the Big Six) are not held to standards, as shown in Figure 2 below.  All of these instruments failed to meet their published specifications, as measured using the ANSI test measurement Standard.  It appears that PSAPs are going to be held to a higher standard.

What is magical or practical with having a low frequency cut off to extend to 250 Hz or lower?  Many currently-fitted hearing aids do not go that low.  In fact, most do not want amplification to go that low because this would amplify low-frequency background noise.  This gives the appearance of being an intended built-in failure feature for a PSAP, especially since most PSAPs are fitted with an open/vented tip, which means that amplification at frequencies this low has been acoustically removed. 


4.2 Frequency Response Smoothness

Figure 3.  A premium hearing aid measured using 1/3 octave bands.  The peak is 13 dB higher than the 2 lower-and higher 1/3 octave band measurements (they average 12 dB).  This instrument would not qualify as a PSAP.  Granted, this was not measured in a diffuse field (measured in a Frye 8000 Hearing aid test chamber) and used the ISTS test signal, but the unusualness of this smoothness requirement is curious.

Figure 3 shows 1/3 octave band measurements of a very popular current premium-priced hearing aid.  According to the smoothness requirement, it would fail.


4.3  Maximum Acoustic Output

This is not the same as for hearing aids (for protection, they use 132 dB).  Actually, isn’t this level a maximum performance standard to avoid uncomfortably loud sounds, rather than a minimum, as specified?


4.4  Distortion Control Limits

Measurement is a hearing aid standard.  Does anyone know what a maximum criterion for distortion is, and how does it provide a minimum performance standard?  Wouldn’t this be nice to know for hearing aids as well?  However, if there is a known threshold description for distortion that is not acceptable for a hearing aid, or to the hearing impaired listener, it appears to be in hiding.


4.5  Self-generated Noise Levels

This measurement requires that the PSAP have programmable capability.  If the PSAP has expansion, or other means to reduce low-frequency noise, and is not programmable, this measurement can be made, but comparison to other programmable devices (which many PSAPs are not) is not a fair comparison.  The assumption should be made that all these measurements can be tested, as outlined, and as provided by the manufacturer.  However, as seen in Figure 4, 32 dB is difficult to achieve even for premium-priced hearing aids.  The full-on equivalent input noise of the right-side instrument exceeds this level.

Figure 4.  Equivalent Input Noise levels for three premium-priced hearing aids as measured full-on.  The instrument on the right would exceed the PSAP required levels.  N3 is the audiogram to which each of the hearing aids was programmed (ANSI Standard Testing Hearing Aids – Part 2).


Category 2

Values that MUST be included.

This category does not include a threshold of acceptable range for the parameter measured.  If this category does not include these, why is it that values MUST be included?


4.6  High Frequency Gain Provided

This is a current hearing aid measurement.  It is difficult to imagine what this tells the consumer.


4.7  Battery Life

The proposed “Standard” states that the establishment of a common metric for battery life allows consumers to more accurately evaluate and compare devices.  This appears to be the first measurement of use to consumers written in this “Standard.”  This follows the current suggested procedure for measurement of hearing aids.  Manufacturers are to report the estimated life for a single operating charge cycle with all optional features turned on and then/also(?) report the estimated battery life for a single operating charge cycle with all optional features turned off.  Current hearing aids don’t have this requirement.  It is unusual for hearing aid manufacturers to specify a particular battery manufacturer for their products (and it is known that each battery manufacturer has different mAmp capacity for the same cell as from another manufacturer), but this “Standard” requires this of PSAPs?  This may not be realistic in that this demand is not even required for hearing aids.  One would expect a premium-priced product to provide this information, but for a PSAP?  Additionally, battery life can change rather dramatically for different environmental listening settings and as the use time lengthens, as shown in Figure 5 for a premium-priced hearing aid.  This suggests again that PSAPs are to be held to a much higher standard than are current hearing aids.

Figure 5.  Measuring and recording battery life is not as simple as using the formula provided.  The formula does not take into consideration higher current drain measurements for certain settings, or the fact that the same size cell from different manufacturers has different mAmp capacities.  How will the consumer know the mAmp capacity of a cell they purchase?  This is not published on the battery packaging.



4.8 Latency

Again, a “not to be exceeded” time of 15 msec is not a standard with regular hearing aids.  Again, a PSAP would be held to a higher standard.


4.9 RF-Immunity

Again, this seems to be a higher standard than with hearing aids.



Category 3

The technological capability or feature shall be reported in the device description.  The specific value/metric for measurement for this value is not within the scope of the “standard”.


What is considered a technological capability or feature?  Is amplification a technological capability or feature?


4.10 Fixed or Level Dependent Frequency Equalization – Tone Control

In a current User Instructional Booklet for a manufacturer of premium-priced hearing aids (Figure 6), this information is not required, nor is it provided.  Again, the PSAP is being held to a much higher standard as none of this is required, nor present in materials to hearing aid customers.

Figure 6.  This provides the technical data on a premium-priced hearing aid that is provided in a User Instructional Booklet.  This is the “comparison” information that hearing aid users generally receive when they purchase a hearing aid.  And, by the way, if they have already purchased in order to get this User Instructional Booklet, there is no longer a pre-comparison opportunity.


4.12 SNR Enhancement

The information asked for here seems to be missing in the requirements for hearing aids.


4.13 Noise Reduction

This is not seen in the User Instructional Booklet to the consumer.  Therefore, how does a consumer make any judgments in traditional hearing aid comparisons?  The fact is, that they don’t.  Someone else makes that decision (rightly or wrongly) for the consumer.


4.14 Feedback Control / Cancellation

Evidence of such feature is not present in the User Instructional Booklet of Figure 6 for premium priced hearing aids, but expected for a PSAP.  Having and stating that such a feature is available may be misleading to the consumer, because none of the feedback/cancellation systems, even in premium-priced hearing aids do not always eliminate acoustic feedback.


4.15 Specification and Reporting

Compliance requires reporting a description of any personalized device functionality for a PSAP, but this is not required of hearing aids.  What good is this anyway, when even with premium-priced hearing aids, the specification, especially the audiogram, provides little or no useful hearing aid fitting information (Figure 7) where the fitting targets are dramatically different by 4 manufacturers for the same audiogram.  Shouldn’t this be required also of hearing aids?

Figure 7.  Using the same audiogram (left), four premium-priced hearing aids provide very different target gains (right).  Somehow, providing audiogram information to fit a PSAP is expected to assist the consumer (if it is available) when it can’t predict an optimum fitting for premium-priced hearing aids.


4.16 Device Coupling to the Ear

Measurements of open or adjustable fit coupling is not in this “Standard” (other than closed fit using a 2cc coupler).  Therefore, what good is the frequency response curve at full-on gain when the majority of PSAPs are fitted using an open mold?  How would this be measured in a 2cc coupler, and if measured that way, what would this tell anyone, including any hearing professional?


4.17 Wireless Connectivity

Again, not required of hearing aids, but mandatory for PSAPs.



Assumed to Apply to All Categories Since These Were Not Identified with Any One Category


4.4.1  Output Distortion

This requirement exceeds hearing aid standards.  Hearing aid standards have no maximum distortion limitation.  Distortion is whatever is measured.  Why 5% for THD+N?  Where is the research for hearing aids to support this level?  This percentage appears to be completely arbitrary.  Digital circuitry in hearing aids generally have THD percentages of less than 1%. 

Because of this, some hearing aid engineers have suggested that they see little use in the THD in the current hearing aid standards, especially since most hearing aids are digital.  So, why put it into PSAP “Standards” where development direction has been toward digital, the same as for hearing aids?


4.4.2  Input Distortion

Again, this is not a requirement of current hearing aid standards.  No part of the current hearing aid standard asks for this measurement.  And, what is magic about 5% THD+N?



  1. Reporting

Wouldn’t it also be proper then that consumers were required to be given this information when purchasing hearing aids?



General “Category” Comments

The “Standard” is meant for PSAPs, but all the measurement procedures are those for hearing aids.  Therefore, this is a hearing aid standard, or as designed, a standard that makes a PSAP a hearing aid.


Informal Listening Tests

Such tests are not required for hearing aids.  The “Standard” states that this is “recommended,” but experience shows that “recommended” soon becomes “required.”

It is not clear which category is the highest.  Is it Category 1 or Category 3?  What is the difference between Category 1, 2, and 3? 

This proposal is more complicated and detailed than are the current hearing aid standards.

How does any of this help the consumer make an informed comparison (especially when they have little or no idea what any of the measurements mean, or how does this help penetrate the untapped market?

Does the following identify this “Standard” correctly?  Let’s make PSAPs meet most hearing aid requirements by requiring testing that may have no direct relationship to consumer satisfaction (remember, satisfaction includes not only listening, but cost, access, time, etc.).  All the suggested measurements do not necessarily make the product better along these lines, but one can argue successfully that they will all increase the end cost to the consumer.  If the measurement requirements are extensive enough, the product will have to be tested just like a hearing aid, adding costs, and moving the PSAP cost and description more in line with hearing aids.  Which group benefits from this, the consumer or the traditional hearing aid manufacturer and dispenser?  This “Standard” appears to be a “protection” publication for manufacturers and the current medical model of distribution, and not for the consumer.

If this “Standard” is voluntary, does this mean that PSAP manufacturers can sell their products without meeting any of these requirements?  If they have to meet any of these requirements, then the “Standard” is not voluntary, but mandated.

It appears that this “Standard”, as written, is an unnecessary intrusion into assisting individuals with mild-to-moderate (and perhaps even to severe) hearing levels, from purchasing products that they find useful to them, that they could purchase OTC.



Acceptance to Hearing Aid Manufacturers and Dispensers

They will like this “Standard”.  It helps maintain the status quo and adds a multitude of restrictions to PSAPs not even suggested for hearing aids.  This “Standard” makes basic amplification devices regulated just like hearing aids, except even more stringently.  It is difficult to see any real differences between this and the current hearing aid Standards that would put PSAPs at a lower measurement involvement level.



  1. ANSI/CTA Standard – Personal Sound Amplification Performance Criteria, ANSI/CTA-2051

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