1. Education and Career at RCA

Olson earned his Ph.D. in electrical engineering and physics from the University of Iowa in 1928 and, in the same year, joined the Radio Corporation of America (RCA), where he worked until his retirement in 1967. During his tenure at RCA, he led research in applied acoustics, electroacoustics, and signal processing, producing over 100 patents and establishing fundamental principles in sound system design.

His contributions ranged from transducer optimization to improvements in sound directivity and speaker efficiency. His book “Acoustical Engineering” (1957) became a reference text for generations of audio engineers and acoustic system designers.

2. Innovations in Microphones and Sound Capture

2.1 Development of the Bidirectional Ribbon Microphone

One of Olson’s most significant achievements in microphone technology was the development of the bidirectional ribbon microphone. Before this breakthrough, conventional microphones had irregular frequency responses and omnidirectional sound pickup, resulting in recordings with excessive background noise.

Olson’s design used a thin aluminum ribbon suspended in a magnetic field, allowing it to generate a signal proportional to the acoustic pressure efficiently. This dramatically improved frequency response and microphone directivity, making it ideal for recording studios and radio broadcasting.

Mathematically, the sensitivity of the ribbon microphone can be expressed as:

Where:

• V is the induced voltage,
• B is the magnetic flux density,
• L is the effective length of the ribbon,
• v is the ribbon’s vibration velocity.

This design enabled bidirectional pickup, with a figure-eight polar pattern, making it useful for stereo recording techniques and ambient noise reduction applications.

2.2 Creation of the Cardioid Polar Pattern

Olson also pioneered the development of the cardioid microphone, whose directional pickup is based on combining front and rear acoustic pressures using acoustic labyrinths. The cardioid directivity significantly improved human voice capture in noisy environments.

The cardioid microphone response is defined by the equation:

Where:

• P(θ) is the acoustic pressure as a function of the angle,
• P0​ is the maximum pressure on the front axis,
• θ is the angle relative to the pickup axis.

This innovation allowed better sound control, reducing off-axis noise pickup and improving audio intelligibility in live and studio environments.

3. Advances in Loudspeakers and Transducers

3.1. Loudspeaker Design Principles

Olson dedicated much of his career to developing more efficient and accurate loudspeaker systems. One of his greatest contributions was optimizing loudspeaker cabinet resonance to minimize unwanted peaks in frequency response.

Using the Helmholtz equation for closed-box systems, Olson refined speaker cabinet designs to enhance low-frequency performance:

​​

Where:

• fr is the resonance frequency,
• c is the speed of sound,
• A is the port area,
• V is the cabinet volume,
• L is the port length.

This analysis significantly improved speaker performance in enclosed spaces and live sound reinforcement systems.

3.2. Development of the Line Array Concept

Olson was one of the first engineers to explore controlled dispersion in linear speaker arrays, laying the groundwork for modern line array systems used in live events.

His work on sound distribution from multiple aligned sources demonstrated that combining multiple small speakers in a vertical line could provide precise directional control, reducing unwanted dispersion and improving coverage in large venues.

The directivity equation for a multi-source aligned system is:

​

Where:

• N is the number of sources,
• k is the wave number,
• d is the distance between sources,
• θ is the observation angle.

This concept evolved into the foundation for modern line array systems, such as the CLa21PLUS by Tecnare, which uses multiple aligned transducers to optimize sound projection in large spaces.

4. Legacy and Modern Applications

Olson’s innovations have influenced multiple areas of sound engineering, from high-directivity microphones to loudspeaker system designs for concerts and studio recordings.

The directional dispersion principles he formulated remain relevant in live sound system design, and his advancements in transducers have served as the foundation for modern high-fidelity sound reproduction technologies.

His work not only defined industry standards but also paved the way for future innovations in digital signal processing (DSP), active loudspeakers, and remote audio control systems.

Conclusion

Harry F. Olson was a pioneer in sound engineering, with contributions ranging from improving sound capture to enhancing sound reinforcement and reproduction systems. His legacy remains relevant today, with technologies continuing to rely on his discoveries and theories.

The evolution of professional audio in concerts, recording studios, and communication systems cannot be understood without Olson’s contributions, whose scientific principles have shaped modern acoustics.