Psychoacoustics and in room target response

The Physics of Perception:

Sound travels as waves, characterized by properties like frequency (pitch) and amplitude (loudness). Psychoacoustics delves deeper, examining how our ears and brains interpret these physical properties to create the auditory experience we know.

Key Concepts in Psychoacoustics:

• Loudness Perception: Our ears don’t perceive loudness linearly. A sound that’s twice the intensity of another won’t necessarily sound twice as loud. Psychoacoustics helps explain this phenomenon, known as the Fletcher-Munson curves, which depict how human hearing perceives loudness at different frequencies.

• Masking: Psychoacoustics explores how different frequencies interact and how masking affects our ability to distinguish sounds and why some are masked, see the full article here: The Masking Effect.

• Localization: We can identify the direction of a sound source with remarkable accuracy. Psychoacoustics examines how our brain uses minute timing and intensity differences between our ears to localize sound.

• Timbre: This quality allows us to distinguish between different instruments playing the same note. Psychoacoustics helps us understand how the complex interaction of overtones and harmonics within a sound wave contributes to timbre perception.

Applications of Psychoacoustics:

The principles of psychoacoustics have numerous practical applications:

• Audio Engineering: Sound engineers leverage psychoacoustics to optimize sound recordings and playback systems. They can manipulate elements like compression and equalization to create a more pleasing listening experience.

• Hearing Aids: By understanding how hearing loss affects sound perception, psychoacoustics helps in designing hearing aids that compensate for these deficiencies and improve speech intelligibility.

• Noise Reduction: Psychoacoustic principles are used to create effective noise-cancelling headphones and active noise control systems, which reduce unwanted sounds by generating cancelling sound waves.

Practicals Studies

Dr. Floyd E. Toole’s studies indicate that listeners tend to prefer a decay in the high frequencies and a smooth change in directivity index (DI), even though the DI should increase in very high frequencies (making the speaker more directive near 7/8 kHz).

To mitigate the conclusion about the significant decay in frequency response, it should be noted that the Revel speaker’s 120° radiation pattern used here is often too wide for many listening spaces and typical listening distances.

This wide dispersion contributes to the desired attenuation, but a more tailored coverage and a better energy balance will have reduce the severity of the frequency response decay.

Bellow this very high frequency decay the radiation must be constant and controlled as lower as possible, without major accidents or diffraction.

With a horizontal polar relative to 0°, it will look like this, with no abrupt change when we lose control at high frequencies:

We select a horn with an opening coverage adapted to the listening distance and room acoustics, while the woofer’s direct radiation pattern remains fixed.
Because of this, their directivity characteristics differ at certain frequencies.
To avoid abrupt changes in directivity, the crossover frequency is chosen where both the horn and woofer have similar radiation patterns: where the horn loses its wide directivity and the woofer starts to become more directional.
This ensures a smooth transition between the two drivers, as explained in the Directivity Match article.

The primary goal is to adapt coverage to listening distance and acoustics without causing an abrupt change in the Directivity Index.

Conclusion:

Psychoacoustics plays a crucial role in shaping our auditory world, but a one-size-fits-all ideal target curve does not exist, as it depends of your acoustics, listening distance and speaker directivity so each “curve” is unique as seen in last point in how to implement my horn and my speaker, do not try to match a generic target curve at listening position.

By understanding the intricate relationship between sound waves and human perception, we can not only appreciate the science behind hearing, but also leverage this knowledge to improve sound design, enhance listening experiences.