Imagine a person with a hearing loss so severe he can’t hear thunder rumbling overhead, yet at the same time, he has hearing so acute he can hear a pin drop. Or imagine a person who can’t hear you talking from just four feet away, who clearly hears a whisper from across a large room. How about a person who can’t hear a car motor running right beside her, yet can hear a single dry leaf skittering along in the gutter 50 feet away?
“Impossible!” you say. “A person could never have such good and bad hearing at the same time.”
This phenomenon is real. Welcome to my world – the bizarre world of extreme reverse-slope hearing loss.
What does reverse-slope mean? Hearing loss is sometimes classified according to the shape it forms on an audiogram. Common yet odd-sounding categories are ski-slope loss, cookie-bite loss, flat loss, reverse cookie-bite loss and reverse-slope (or reverse-curve) hearing loss. (For more about differences in hearing loss, see “Causes/Kinds of Hearing Loss” on the “Articles” link at www.hearinglosshelp.com.)
By far, the most common kind of hearing loss is the typical ski-slope loss where the line on the audiogram slopes down to the right as seen in Figure 1. In contrast, a reverse-slope loss, as its name implies, does the reverse and slopes up to the right as seen in Figure 2. As a result, this kind of hearing loss is sometimes referred to as an up-sloping loss, a rising loss or even a low-frequency hearing loss, but is usually called reverse-slope hearing loss.
The occurrence of reverse-slope loss is relatively rare. Just as there are various degrees of ski-slope hearing losses, there can be an enormous difference in hearing between a mild, gently-sloping reverse-slope hearing loss (Fig. 3) and a severe or profound, steeply-sloping reverse-slope loss (Fig. 4).
For practical purposes, we can group reverse-slope hearing losses into three basic classes. Class one has a gently up-sloping line in the standard audiometric frequencies between 250 and 8,000 Hertz (Hz), as seen in Figure 3. In this class, low-frequency hearing loss ranges from mild to moderately severe. Class one curves are often seen in people with the beginning stages of Meniere’s disease. Less common is class two, in which there is a moderate to severe hearing loss in the frequencies below 1,000 Hz, with hearing becoming virtually normal somewhere in the range of 2,000 to 6,000 Hz (Fig. 2). It is in class two that the differences between reverse-slope losses and ski-slope losses really become apparent. In class three, the rarest form of reverse-slope loss, we see a steeply up-sloping line ranging from severe to profound hearing loss – 70 to 110 decibels (dB) in the low frequencies – to incredible hearing in the very high frequencies, those above 8,000 Hz (Fig. 4). Class three hearing is quite bizarre, with a “weird hearing zone” that ranges over 100 dB between the faintest low-frequency sound and the faintest high-frequency sound a person can hear.
My hearing loss spanned an incredible range of 105 dB; no wonder people were always confused about what I could and could not hear! For example, my former mother-in-law wouldn’t believe my hearing was as bad as it was because when she whispered to conceal something from me, I could easily hear her. Whispers are generally high-frequency sounds, which I can hear. She never caught on that if she just spoke in a normal voice, I wouldn’t have understood a thing! When I was in my early 20s, my hearing ranged from 75 dB at 1,000 Hz to negative 30 dB in the frequencies above 16,000 Hz (Fig. 4). The negative decibels represent super-acute hearing. Since I was able to hear “silent” dog whistles, some said I had “dog ears” hearing.
Mild reverse-slope hearing losses are relatively rare, and even more so are extreme reverse-slope hearing losses like mine. The former head of the Kresge Institute in Louisiana, Dr. Charles Berlin, has studied this kind of hearing loss extensively and estimates that out of the 31 million Americans with hearing loss, around 3,000 may have my unusual kind of reverse-slope hearing loss.
Causes of Reverse-Slope Hearing Loss
Fortunately, this pattern of hearing loss seems to be nonsyndromic, having no other conditions or syndromes associated with it. However, some diseases may result in reverse-slope hearing loss, such as measles, chicken pox and Meniere’s disease.
Whereas classic Meniere’s disease may result in a class one reverse-slope hearing loss, at least in the beginning stages, the most common cause of reverse-slope hearing losses, particularly in classes two and three, is genetic.
Reverse-slope hearing loss has run in my family for the past four generations. Those that I know of who have it include my maternal grandfather, mother, brother, younger daughter, brother’s older son and me. Could it be that extreme reverse-slope hearing loss is a dominant genetic trait? It certainly seems to be in my family. Each person born in my family has a 50 percent chance of having this kind of hearing loss.
Whether reverse-slope losses get worse with time depends on what caused the loss in the first place. The hearing loss that Meniere’s causes may start out as a class one reverse-slope loss and over time evolve into a reverse cookie-bite or flat loss, and ultimately into some degree of a severe or profound ski-slope loss. Hereditary losses seem to go through three distinct stages. Let me illustrate with some of my own experiences as well as those of others.
Stage 1: The first stage occurs from birth to around five years of age. Although there may be some degree of hearing loss at birth, hearing in the lower frequencies rapidly decreases until around age five. My parents didn’t discover I had a hearing loss until I was about four or five because I had developed excellent speech reading skills of which my parents were completely unaware. One day my dad, who was standing behind me so I couldn’t speech read, asked, “Do you want to come for a ride in the car with me?” I totally ignored him and continued playing on the floor. He knew something was wrong because I loved riding in that ‘29 Buick! Another time he asked me if I wanted some ice cream – which I still love – and again I ignored him. It was at this point that my parents had my hearing tested and discovered I had a severe hearing loss!
Stage 2: The second stage begins around age five and continues without significant change to around age 50, as long as there are no other significant damaging factors like noise or ototoxic drugs, for example. I learned to adapt to my strange hearing loss and the coping strategies that worked for me as a teenager worked throughout most of my adult life.
Stage 3: At about age 50 and progressively more as we get older, our hearing loss changes, not particularly due to our reverse-slope hearing loss, but rather due to the normal deteriorating effects of aging on our precious high-frequency hearing. Between ages 50 and 60, I lost much of my excellent high-frequency hearing. You can see this by comparing my audiogram taken at around age 21 (Fig. 4) with my current audiogram (Fig. 5) taken at age 59.
Loss of high-frequency hearing as we age is normal and to some extent, inevitable. Figure 6 plots curves of the average, progressive high-frequency hearing loss from age 40 (top line) to age 80 (bottom line).
People with a typical ski-slope loss have already lost their high-frequency hearing but retain their low-frequency hearing. Thus as they age, they don’t have much high-frequency hearing left to lose. In contrast, those of us with extreme reverse-slope loss have most of our residual hearing in the high (and very high) frequencies throughout middle age and can expect to lose some of our high frequency hearing in the later half of life.
The Blessing of Perfect Speech
One pleasant surprise is that people with severe reverse-slope losses have perfectly-normal or near-normal speech. Imagine a person that is essentially deaf, yet has flawless enunciation, perfectly-formed and well-modulated speech, all without having had any speech therapy.
Shirley, a woman with reverse-slope loss explains, “Because I have high-frequency hearing, my voice has never been affected by my hearing loss, although my hearing loss is profound.”
It’s the same with me. Because my speech is indistinguishable from the speech of people with normal hearing, I’ve had many people refuse to believe how bad my hearing really is.
One woman I met, herself hard of hearing, after hearing me speak, exclaimed, “Do you realize that your speech is absolutely perfect? You must have worked very hard to perfect your tone like that, what with growing up hard of hearing.” The truth is I’ve never had speech therapy and I’ve never needed it. The reverse-slope secret to normal speech is our ability to hear all speech frequencies, especially the high-frequency consonants so important in understanding speech, such as “s,” “f,” “sh,” “ch,” “t” and “th.”
Life with a Reverse-Slope Hearing Loss
Having a class two or three reverse-slope loss makes for some interesting experiences. Here are a few typical scenarios and how I and others have coped.
I don’t hear appliances running. I have to put my hands on household appliances (refrigerator, washer, dryer, furnace, etc.) to feel the vibrations in order to know if they are running. However, I can readily hear the faint click of the relays from across a room as they kick in or out to start/stop these appliances but I can’t tell whether they just started or just stopped.
I hear whispers very clearly even from across a room. In school, I used to hear kids whispering from across the classroom yet I couldn’t hear the teacher talking only a few feet away. It always puzzled me that the teachers never heard all the whispering that to me was so loud. Since whispering seemed so loud to me, I always use a low voice instead of a whisper and, to me, it sounds very faint like a whisper should. However, to my chagrin, everyone around can hear me “whispering.”
Since I can’t hear my car’s motor running, sometimes when I am parked I may try to start my car a second time thinking it hasn’t started. The suddenly-swiveled heads of the people nearby tell me that I just ground the gears on the starter – again! Now, I always look at the tachometer first. If it’s not reading 0, I know the car is running.
The screech of train wheels on the tracks is so loud to me that it hurts my ears, yet to most people this does not sound loud. Imagine not being able to hear the loud roar of a train bearing down on you, yet getting headaches from the painfully loud screech of the train wheels against the tracks as the train goes around a curve.
I can easily hear the high-frequency 15,734-Hz whine produced by the fly-back transformer of a television from anywhere in the house, and even from outside the house, yet I have to put my ear about six inches from the television’s speaker in order to understand any speech from it if the volume is set to normal hearing levels.
To me, certain insects chirping from a block away (even just one insect) produce a racket loud enough to drown out the voice of a person standing almost nose-to-nose with me. Oddly, the person with normal hearing with whom I may be talking either can’t hear that insect at all, or can only hear it very faintly!
I hear some birds singing and chirping away, but not others. For example, I have never heard the low-frequency sounds of an owl hooting or a Mourning Dove cooing (although I have a flock of Mourning Doves right outside my back door), yet I can easily hear a male hummingbird’s high-pitched angry squeaks as it chases off a competitor, or the wonderful trilling sounds it makes as it power dives to impress its prospective mate.
Although there are many coping skills that are common to all kinds of hearing loss, many of them are designed for the needs of people with ski-slope losses. A person with reverse-slope losses may need just the opposite advice, as in these three examples.
1. People with ski-slope loss often don’t want others to speak louder but rather to enunciate more clearly. People with a ski-slope loss hear the loud vowel sounds but not the soft consonants. They can hear people talking with no problem but because most of the intelligibility of speech is in the consonants, they don’t understand what people are saying. Words sound muffled because they don’t hear the high-frequency sounds. Thus they primarily want more clarity, not more volume.
People with reverse-slope losses, however, need more volume in order to hear speech in the first place. We can hear the soft, high-frequency consonant sounds. To us, speech is thin, almost inaudible and often sounds like whispers. For example, as I approach someone talking, the first sounds I hear are the high-frequency voiceless “s” sounds. We do not really hear a person talking until we get very close so we can hear the “voiced sounds.” Thus we typically need more volume.
2. People with ski-slope losses hear men better than women because men have louder, lower-pitched voices. Women and children with their higher-pitched (and often softer) voices are much more difficult for them to hear and understand.
Again, the opposite is true for those of us with reverse-slope losses. Since we hear the higher-frequency sounds best, we typically hear women’s voices better than men’s voices. I much prefer talking to women as their higher-pitched voices are more in tune with my ears. If men speak in a high falsetto voice, I then hear them well too. Though, I must confess, it’s not easy asking a man to speak in a high falsetto voice!
3. For people with a ski-slope loss, low-frequency noise drowns out speech. Speech is lost in the racket caused by the noise in factories and mills and by the air conditioning/heating fans in our homes, offices and schools, thus people with ski-slope losses have to shout over all the low-frequency noise around them.
However, for us reverse-slopers, since we don’t hear low-frequency sounds well, we clearly hear the people “shouting” over low-frequency background noise which we can’t hear at all. In contrast, we cannot hear speech through all the high-frequency sounds around us. For us, baneful background noise consists of running water, clinking cutlery, rustling and crumpling papers and people whispering.
There are many other fascinating aspects of reverse-slope hearing loss and if you would like to learn more, including issues such as diagnosing (and misdiagnosing) reverse-slope losses, testing for and fitting hearing aids, cochlear implants and assistive devices for people with reverse-slope losses and other topics, visit www.hearinglosshelp.com/articles /reverseslopelong.htm.
If you or someone you know has a reverse-slope loss and would like to join an information and support e-mail list for people (and parents of children) with reverse-slope hearing loss, send a blank e-mail to RSHL-subscribe@yahoogroups.com.
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