Analog Vs. Digital Hearing Aids

Digital Technology is Unable to Deliver Sound in a Way That Makes Us Feel at Home in the World.

Analog Hearing Aids in the age of Digital

The advent of digital signal processors (DSPs) has been nothing short of revolutionary. In two quick decades, it has become inconceivable to envision a world without smartphones, digital cameras, bluetooth headsets, ipods, mp3 players, and countless other devices.

In hearing aids, DSPs offer the ability to tailor amplification and manipulate sound, enabling features like background noise suppression and wireless connectivity. Digital aids are also cheaper to manufacture, so it is easy to see why digital hearing aids have come to dominate the market.

But as digital hearing aids came onto the market – one thing became clear, they could not faithfully reproduce natural sound. Most people could tell the difference, and not all could adapt – they just didn’t like what it did to voices and music.

Patients would complain when wearing digital hearing aids

  • Familiar voices don’t sound like we remember them
  • Voices often sound tinny, everything sounds like phone call
  • Music lacks the richness and emotive connection.

That these complaints have continued for decades – makes the decision of the industry to abandon analog hearing aids even more surprising.

Quotes

Huge step down from vinyl,” Young said. Each step eliminated levels of sonic detail and shading by squeezing down the amount of information contained in the package in which music was delivered. Or, as Young told me, you are left with “5 percent of the original music for your listening enjoyment.

– Neil Young

Analog vs Digital – The Science

Analog vs Digital - The Science

In one way, this is not surprising. The engineers and scientists who design digital hearing aids are competing against millions of years of evolution.

Sound waves are created by vibrations or oscillations of objects, such as musical instruments, vocal cords, or speakers. The waveforms produced by different sources combine and interact to create the overall sound that we perceive.

Real-world sounds are more complex and consist of a mixture of different frequencies and waveforms. For example, speech, music, and environmental sounds have a wide range of frequencies, amplitudes, and harmonic interactions, that give them their unique characteristics.

Digital devices thus have to re-create the activity that each of our brains and ears have performed together for decades. Considering that there are over 25,000 nerve endings in each ear, the processing power required to truly recreate analog sound is only possible with high end studio equipment to digitize the entire frequency range..

But as we move down into the consumer space, we can quickly see that digital amplification produces a less and less accurate recreation of the natural sound.

As devices become smaller and less powerful (like hearing aids) such degradation of sound quality is easily detectable. Simply put, It is why people on the phone, sound like they are on the phone

Quotes

We worry that the humanity is being drained out of music.

Tim Cook, Apple CEO

Hear the difference

The reason digital hearing aids are unable to reproduce the world we know comes down to three main issues: Sampling rate, Sampling losses and noise, and Latency.

1 Sampling Rate

Digital audio signals are sampled at a specific rate, known as the sampling rate, which determines the frequency range that can be accurately captured.

With limitated processing power, digital,hearing aids to reduce the amount of information they process. This is done by reducing the eliminating low and high frequencie, reducing the “number of samples per second (hz), capturing a smaller range of decibels (bit rate).

With entire bands of low and high frequencies ignored altogether. The loss of sound quality in Digital Amplification is due to three main reasons.

Sampling Rate

2 Digital losses and noise

Digital audio signals are represented using a finite number of bits, which means that the continuous analog waveform is converted into a series of digital bands. During the sampling stage, some portion of the sound will remain uncaptured. Subsequently when quantized sound is output and then passed through an analog filter – digital amplification can insert small during the sampling stage,

If the sampling rate is too low or inadequate, it can result in aliasing, which causes distortion or artifacts in the reproduced audio.

Digital losses and noise

3 Latency (delay)

Your brain processes analog sound instantly, while even the fastest computers will introduce a miniscule time delay.

Because most people still have some hearing, your brain is forced to combine the sound you hear naturally, with the digitally amplified sound at a slight delay. This delay is known as latency.

Analog hearing aids by contrast – are able to process sound instantly – and hence your brain hears a single sound signal – not two signal offset by milliseconds.

In speech as in music, timing is everything, and even milliseconds matter. This is why voices often sound unnatural or tinny, and music feels flat. In fact, studies have shown that digitally amplified hearing aids result in an audio signal that is harder for brain to process.

Here we see an example from the famous Rudyard Kipling poem, IF.

Latency (delay)
Male Voice

Male Voice

  • Normal Hearing
  • Digital Hearing Aids (10ms latency)
Female Voice

Female Voice

  • Normal Hearing
  • Digital Hearing Aids (10ms latency)

Quotes

We’ve gained control, but we’ve lost the sound. The sound is gone.

– Neil Young

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