Psychoacoustics

Psychoacoustics is the study of how we hear and understand sound. It looks at how our minds and ears work together to process noises like music, speech, and even unwanted sounds such as noise. This field brings together many areas of science, including psychology, physics, biology, and engineering.

By studying psychoacoustics, scientists can learn how people hear different sounds and why some sounds feel nicer or more uncomfortable than others. This knowledge helps make better audio technology, such as headphones and speakers, and helps design places where it is pleasant to listen.

Psychoacoustics also helps us understand how we recognize speech and music. This is important for technologies like voice assistants and music streaming services. It helps explain why certain sounds can change our mood and how we can use sound to improve communication and design.

Background

Hearing is more than just sound waves moving through the air. When we hear something, the sound travels to our ears and turns into signals that our brain can understand.

Our inner ear helps change sound waves into signals for the brain. This is why some sounds can feel the same, even if they are a little different. Tools like MP3 files use this idea to make files smaller. Our ears also react differently to loud and quiet sounds. This is why things sound louder or softer depending on how loud they are. This property is called loudness and is used in telephone systems and noise reduction technology.

Limits of perception

Our ears can hear sounds between about 20 to 20,000 Hz, but this range can get smaller as we get older. Very low sounds, below what we usually call noise, can sometimes be felt through our sense of touch. Our ears are very sensitive and can pick up tiny changes in sound, from quiet noises to loud ones.

We can notice small changes in pitch, especially when two similar frequencies make a pulsing sound. Loudness is measured on a special scale, so our ears hear differences in volume and pitch in unique ways. Research has helped scientists learn more about how we hear different sounds.

Sound localization

Main article: Sound localization

Sound localization is how we know where a sound is coming from. Our brain looks at tiny differences in loudness, tone, and timing between the two ears to figure this out. We can describe a sound’s position in three ways: side to side, up and down, and how far away it is. People, like most animals with four legs, are good at telling where sounds are coming from side to side but not as good up and down because our ears are placed the same on both sides. Some owls have ears placed unevenly, which helps them detect sounds from all directions, useful for finding food in the dark.

Masking effects

Main article: Auditory masking

When you try to hear a quiet sound and a louder sound is playing, the quiet sound may be harder to hear. This is called masking. The louder sound that makes it harder to hear the quieter one is called the masker.

Even if the quiet sound is weaker, it can sometimes still be heard. Masking can happen when both sounds play together, like when someone whispers while another person shouts. It can also happen just before or after a loud sound, like a clap, making sounds around it harder to hear. This idea is used in some music file formats to make files smaller.

Missing fundamental

Main article: Missing fundamental

When we hear a series of related tones, such as double, triple, and quadruple the pitch of a certain note, our ears often seem to hear an extra tone that isn't really being played. This is called the missing fundamental. It shows how our brain helps us understand sound.

Music

Psychoacoustics studies how we hear and feel music. It helps us understand why some sounds sound nice or calm. Some people use these sounds in music therapy to help others feel better.

Irv Teibel's Environments series LPs from 1969 to 1979 were early examples of sounds made to help improve mood and focus.

Applied psychoacoustics

Psychoacoustics works closely with computer science. Important pioneers like J. C. R. Licklider and Bob Taylor studied this field. Companies like BBN Technologies began by focusing on acoustics before creating early networks such as the packet-switched network.

Today, psychoacoustics helps make better audio technology. It is used in audio formats like MP3 and Opus, which let music be stored in smaller files. It also helps design new audio systems for theaters and homes. It is used in applications such as sonification, computer games, drone control, and image-guided surgery. Musicians use it to improve sounds, and car makers use it to design engines and doors that sound pleasant.

Perceptual audio coding

See also: Data compression § Perceptual audio coding

Psychoacoustic models help make music files smaller by taking away parts of the sound that our ears cannot hear well. This makes files much smaller, about one-tenth to one-twelfth the size of the original, while keeping most of the sound quality. Formats like Dolby Digital, MP3, Opus, Ogg Vorbis, AAC, WMA, MPEG-1 Layer II, and ATRAC use this method.

Our ears can only hear certain sounds, and psychoacoustics studies these limits. This helps audio tools focus on the sounds we notice most and ignore the ones we don’t, which makes files smaller without losing important sound.