Most people probably associate a tinnitus with a high pitched ringing. However, the type of noise perceived by those affected is more diverse. It may also sound like a hiss, clicking, knocking, roaring, humming or a buzzing. (page link Wikipedia definition tinnitus)
On our page we want to go into more detail about a form of tinnitus, which manifests itself in the perception of a humming tone, the low-frequency tinnitus.
This form of tinnitus is still relatively unknown, although historical mentions of „buzzing“ or „humming“ in the ear date back to 400 BC. Even audiologists often do not know that the symptoms described by their patients could be a low-pitched tinnitus, since the low-frequency tinnitus manifests different characteristics compared to the more common high pitched tinnitus. Research into this special form of tinnitus is still in its infancy.
Initial assumptions and suspicions of hum-tone-sufferers
People affected by a low frequency tinnitus often assume, that the perceived hum is an actually existing tone that is caused by external sources (page link Brummtöne und Störgeräusche)
Many people suffering from low-pitched tinnitus perceive the humming tone as a tone that reaches the ear from the outside (in contrast to high-frequency tinnitus, which is mostly perceived as an internal sound). This confirms the assumption of many affected, that the perceived noise cannot be a tinnitus. Some categorically reject a tinnitus as an explanation for the perceived humming tone, which often results in an unsuccessful search for a cause over a long period of time.
Technical industrial plants, such as factories, power plants or wind turbines that could cause a humming sound are often suspected as a cause of the hum. If there are no technical plants of this type in the immediate vicinity, radio systems in general (WLAN, mobile phones, radar) are assumed to be the possible cause of a perceived humming sound. If only a single person hears a humming sound in a surrounding, it is very often assumed that this person has particularly good hearing. Even the theory of a global humming sound (page link „Taos Hum“) has been discussed for some time.
Externally existing acoustic hum-tone or low-frequency tinnitus?
All initial assumptions can be checked using appropriate measurement technology. You can find a written manual for measuring with the Spectroid app here (page link Measuring with Spectroid). Humming tones can be visualized very well with a reasonably modern smartphone or tablet.
There is also a manual on this website on how to determine the frequency of your personal perceived hum-tone (page link: determining the hum-tone frequency). Having determined your perceived hum-tone frequency you are now able to compare this with the measured hum-tones by Spectroid within your environment.
If the Spectroid App cannot detect a hum-tone that corresponds with your determined perceived hum-tone frequency, it could be a first indication of a low-frequency tinnitus.
You can also use the visual display of hum-tones in the Spectroid App to check whether hum sounds that are actually present in your surroundings for some time may trigger an internal hum tone (low-pitched tinnitus).
Characteristics that might indicate a low-pitched tinnitus and special similarities:
The perceived humming tone can be momentarily interrupted by a quick shake of the head, chattering of your teeth, or masking noises (an actual humming sound would always be heard).
The person affected is almost always the only one who perceives the hum in their environment, often a humming tone cannot be measured in the perceived frequency.
The hum is rarely heard outside or in connection with background noises.
Many only hear their humming sound in certain and relatively quiet places.
The humming sound is not always heard continuously, there can also be longer periods of time, where the hum is not present.
The volume is not always the same, sometimes the tone pulsates, but the frequency almost always remains the same.
A lot of hum-tone-affected describe their tone similar to that of a diesel truck engine heard from a distance.
Most of those affected report a „travel effect“, which means that the hum is perceived weaker or not at all for some time during and/or after being on holiday or away from their usual place of residency.
If the ear is sealed with a finger, the humming sound disappears for many hum-hearers. This often leads to the wrong conclusion that the humming tone must be caused by an external source. A similar effect can often be achieved with earplugs.
Hum tones are also heard in Faraday cages (Page link rooms shielded from electromagnetic fields). Therefore, radio applications can be excluded as a source.
The internal hum can be triggered with a softly played sine tone of a frequency range that is similar to that of the perceived humming sound. The external hum-tone triggers an internal hum. This can be checked easily by everyone using a tone generator. Once the internal hum is triggered, the person who perceives the hum can no longer distinguish if it is the internal or external hum they hear. This was only recently discovered in a study with 120 hum-hearers. People who have healthy hearing, however, do not have any trouble hearing whether or not an actual hum-tone is played.
Short-term sounds of various kinds, e.g. from cars / trucks, airplanes, heat pumps or agricultural machinery can trigger your own hum-tone permanently or for a certain time. This means that the actual sound has long since disappeared, but the inner hum-tone remains.
Most people with a low-pitched tinnitus do not usually have above-average hearing characteristics. (page link: Dutch examination of hearing ability of hum-tone-sufferers)
Simple Hum-Tinnitus self Test:
A simple test to check if you may have deep-tone tinnitus.
When hearing a deep-tone hum, the question arises whether it is an internal and / or an external tone and which ear is affected. There is a relatively simple test that does not require any tools or technical equipment:
If you generally want to know whether the sound is coming from inside or outside, first shut both ears as tight as possible with the palms of your hands on the auricles and move the middle and index fingers in opposite directions or gently drum on the head.
A booming (or humming) noise should be heard, if not, then press the palms of the hands a little harder on the ears and / or drum your fingers instead of just moving them. You do this for about 10 seconds and take your hands off your ears again. If the humming occurs in the ear, and if the test is carried out correctly, it will then be interrupted for at least approx. 5 – 10 seconds or even a little longer. If it is not interrupted, then it is a normally audible ambient noise. After the interruption, the humming gradually builds up again over a period of a few seconds to a few minutes, becomes a little louder for a short time and finally levels off again at the usual volume. In order to determine which ear is affected, the test is carried out one-sided one after the other.
This test probably does not work equally well for everyone, especially if there is a real ambient noise that comes close to the frequency of the internal humming tone, but this simple test has proven itself in practice.